Infusion devices and related methods and systems for regulating insulin on board

ABSTRACT

Infusion systems, infusion devices, and related operating methods are provided. An exemplary method of operating an infusion device capable of delivering fluid to a user involves determining a current amount of active fluid in the body of the user, determining a threshold amount of active fluid in the body of the user, and automatically altering operation of the infusion device to modify delivery of the fluid to the user based on a relationship between the current amount and the threshold amount.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.14/261,272, filed Apr. 24, 2014. The subject matter described herein isalso related to the subject matter described in U.S. patent applicationSer. No. 14/261,266, filed Apr. 24, 2014.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally tomedical devices, and more particularly, embodiments of the subjectmatter relate to controlling operations of a portable electronic device,such as a fluid infusion device.

BACKGROUND

Infusion pump devices and systems are relatively well known in themedical arts, for use in delivering or dispensing an agent, such asinsulin or another prescribed medication, to a patient. A typicalinfusion pump includes a pump drive system which typically includes asmall motor and drive train components that convert rotational motormotion to a translational displacement of a plunger (or stopper) in areservoir that delivers medication from the reservoir to the body of auser via a fluid path created between the reservoir and the body of auser. Use of infusion pump therapy has been increasing, especially fordelivering insulin for diabetics.

Continuous insulin infusion provides greater control of a diabetic'scondition, and hence, control schemes are being developed that allowinsulin infusion pumps to monitor and regulate a user's blood glucoselevel in a substantially continuous and autonomous manner, for example,overnight while the user is sleeping. Regulating blood glucose level iscomplicated by variations in the response time for the type of insulinbeing used along with each user's individual insulin response.Predictive algorithms may be utilized to provide estimations of thefuture blood glucose levels as an aid in regulating the blood glucoselevel. Rather than continuously sampling and monitoring a user's bloodglucose level, which may compromise battery life, intermittentlyobtained blood glucose data samples may be utilized for determiningestimations of future blood glucose levels.

Problems arise, however, when one or more blood glucose data samplesintended for input to a predictive algorithm are corrupted, lost, orotherwise invalid, for example, due to noise, transmission errors, orthe like. For example, in the case of recursive prediction algorithms,the prediction algorithm may be reset to eliminate the so-called “bad”data from undesirably influencing the device operation. Such an approachalso incurs the lag time required for the prediction algorithm toachieve a desired level of reliability, and thus, would result in aninability to provide predictive control for periods of time.

BRIEF SUMMARY

An embodiment of a method of operating a device is provided. Anexemplary method of operating an infusion device operable to deliverfluid influencing a physiological condition in the body of a usercomprises determining a current amount of active fluid in the body ofthe user, determining a threshold amount of active fluid in the body ofthe user, and automatically altering operation of the infusion device tomodify delivery of the fluid to the user based on a relationship betweenthe current amount and the threshold amount.

In one embodiment, an infusion device is provided that comprises a motoroperable to deliver fluid to a body of a user and a control modulecoupled to the motor to operate the motor to deliver the fluid based ona difference between a current measurement value for the physiologicalcondition and a target value for the physiological condition when thecurrent measurement value is greater than the target value. When thecurrent measurement value is less than or equal to the target value anda current amount of active fluid in the body is less than a lowerthreshold amount, the control module operates the motor to deliver thefluid in a manner that regulates the current amount of the active fluidin the body of the user to the lower threshold amount. Conversely, whenthe current measurement value is less than or equal to the target valueand the current amount of active fluid is greater than an upperthreshold amount, the control module suspends operation of the motor.

In another embodiment, a method of operating an infusion device operableto deliver insulin to a body of a user is provided. The method involvesidentifying a minimum insulin on board for the user, identifying acurrent insulin on board for the user, generating a delivery commandconfigured to regulate the current insulin on board to the minimuminsulin on board, and operating the infusion device in accordance withthe delivery command.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures, which may beillustrated for simplicity and clarity and are not necessarily drawn toscale.

FIG. 1 depicts an exemplary embodiment of an infusion system;

FIG. 2 depicts a plan view of an exemplary embodiment of a fluidinfusion device suitable for use in the infusion system of FIG. 1;

FIG. 3 is an exploded perspective view of the fluid infusion device ofFIG. 2;

FIG. 4 is a cross-sectional view of the fluid infusion device of FIGS.2-3 as viewed along line 4-4 in FIG. 3 when assembled with a reservoirinserted in the infusion device;

FIG. 5 is a block diagram of an exemplary control system suitable foruse in a fluid infusion device, such as the fluid infusion device ofFIG. 1;

FIG. 6 is a block diagram of an exemplary sensing arrangement suitablefor use in the control system of FIG. 5;

FIG. 7 is a block diagram of an exemplary pump control system suitablefor use in the control system of FIG. 5;

FIG. 8 is a flow diagram of an exemplary control process suitable foruse with the control system of FIG. 5;

FIG. 9 depicts a table of measurement sequences suitable for use withthe control process of FIG. 8;

FIG. 10 depicts a table of the measurement sequences of FIG. 9 aftermodifying unusable measurement samples and determining a predictedmeasurement value in accordance with one or more exemplary embodimentsof the control process of FIG. 8;

FIG. 11 depicts block diagram of an exemplary pump control systemsuitable for use in the control system of FIG. 5;

FIG. 12 depicts a flow diagram of an exemplary delivery suspensionprocess suitable for use with the control system of FIG. 11;

FIG. 13 depicts a flow diagram of an exemplary delivery resumptionprocess suitable for use with the control system of FIG. 11 inconjunction with the delivery suspension process of FIG. 12;

FIGS. 14-19 are graphs depicting exemplary relationships between auser's current measurement values with respect to time for variousexemplary embodiments of the delivery suspension process of FIG. 12 inconjunction with the delivery resumption process of FIG. 13;

FIG. 20 depicts a flow diagram of an exemplary insulin on boardmonitoring process suitable for use with the control system of FIG. 11;

FIG. 21 depicts a flow diagram of an exemplary insulin on board controlprocess suitable for use with the control system of FIG. 11 inconjunction with the insulin on board monitoring process of FIG. 20;

FIG. 22 is a block diagram of an exemplary closed-loop control systemsuitable for use with the control system of FIG. 11;

FIGS. 23-24 are graphs depicting exemplary relationships between insulinon board and insulin infusion rate for one exemplary embodiment of theinsulin on board monitoring process of FIG. 20 in conjunction with theinsulin on board control process of FIG. 21;

FIG. 25 depicts a flow diagram of an exemplary insulin on boardsuspension process suitable for use with the control system of FIG. 11;and

FIGS. 26-28 are graphs depicting exemplary relationships betweenglucose, insulin on board, and insulin infusion rate for one exemplaryembodiment of the insulin on board suspension process of FIG. 25.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

While the subject matter described herein can be implemented in anyelectronic device that includes a motor, exemplary embodiments describedbelow are implemented in the form of medical devices, such as portableelectronic medical devices. Although many different applications arepossible, the following description focuses on a fluid infusion device(or infusion pump) as part of an infusion system deployment. For thesake of brevity, conventional techniques related to infusion systemoperation, insulin pump and/or infusion set operation, and otherfunctional aspects of the systems (and the individual operatingcomponents of the systems) may not be described in detail here. Examplesof infusion pumps may be of the type described in, but not limited to,U.S. Pat. Nos. 4,562,751; 4,685,903; 5,080,653; 5,505,709; 5,097,122;6,485,465; 6,554,798; 6,558,320; 6,558,351; 6,641,533; 6,659,980;6,752,787; 6,817,990; 6,932,584; and 7,621,893; each of which are hereinincorporated by reference.

Embodiments of the subject matter described herein generally relate tofluid infusion devices including a motor that is operable to linearlydisplace a plunger (or stopper) of a reservoir provided within the fluidinfusion device to deliver a dosage of fluid, such as insulin, to thebody of a user. As described in greater detail below, in exemplaryembodiments, the dosage commands that govern operation of the motor areinfluenced by not only a current (or most recent) measurement of acondition in the body of the user, but also a predicted value (oranticipated measurement) for that condition in the body of the user atsome point in the future. For example, an insulin dosage command may bedetermined based on a current blood glucose measurement for the user ina manner that is influenced by a predicted (or anticipated) bloodglucose level in the body of the user 30 minutes into the future. Inthis regard, the insulin dosage command determined based on the user'scurrent blood glucose level may be adjusted, modified, enabled and/ordisabled based on the predicted blood glucose level to increase thelikelihood (if not ensure) that the user's blood glucose level ismaintained within an acceptable range of values going forward. While thesubject matter is described herein in the context of a fluid infusiondevice for purposes of explanation, the subject matter is notnecessarily limited to such an implementation. For example, thepredicted value may be determined and/or utilized by a monitoring deviceto determine when and/or how the monitoring device should be operated toalert or otherwise notify a user (or one or more other individuals) of acondition in the body of the user, an operational status of an infusiondevice or another medical device associated with the user, and/or thelike.

As described in greater detail below in the context of FIGS. 5-10, inexemplary embodiments, a predicted blood glucose level is calculated orotherwise determined as a sum of the user's current blood glucose leveland a weighted estimate of the trend in the user's blood glucose levelthat is determined based on previously obtained blood glucose levels forthe user. In exemplary embodiments, the estimate of the trend iscalculated as a weighted sum of the differences between consecutivemeasurements that precede the current measurement. Thus, previouslyobtained blood glucose measurements for the user are stored or otherwisemaintained for use in calculating the estimate of the trend in adeterministic manner rather than a recursive manner. In exemplaryembodiments described herein, when one or more of the previouslyobtained blood glucose measurements are unusable for determining thepredicted value, one or more other blood glucose measurements are usedto obtain a modified measurement value that is substituted or otherwiseused in place of the unusable blood glucose measurement. In this manner,measurements that are deemed invalid, unacceptable, or otherwiseunreliable are excluded from use in determining the predicted value.Rather than disabling or otherwise resetting the prediction and/orwaiting until a full sequence of consecutive usable measurements isavailable, the modified measurement sequence is utilized to calculatethe predicted value and continue operation of the device in a mannerthat is influenced by the predicted value.

As described in the context of FIGS. 11-19, in one or more embodiments,the operation of the infusion device is automatically altered or changeto modify the delivery of fluid to the user when both the predictedvalue for a physiological condition of the user violates an applicablethreshold value and the current value for the physiological conditionalso violates its corresponding applicable threshold value. In thisregard, the operating mode for the infusion device is automaticallyadjusted or otherwise transitioned from an operating mode where deliveryof the fluid is enabled (e.g., a delivery mode) to an alternativeoperating mode where delivery of the fluid is disabled or otherwisesuspended (e.g., a suspend delivery mode), and vice versa. For example,the infusion device may automatically transition from a normal deliverymode used to regulate the blood glucose level of the user to analternative operating mode where fluid delivery is suspended, disabledor otherwise altered in response to determining that the current glucosemeasurement value for the user is less than a first threshold value andthe predicted glucose value for the user is less than a second thresholdvalue.

In the suspend delivery mode, any delivery (or dosage) commands that mayotherwise be determined using the normal delivery control scheme (e.g.,open-loop delivery commands to provide a basal infusion rate,closed-loop delivery commands based on the user's current glucosemeasurement value, or the like) are disabled or otherwise deactivated toreduce the likelihood and/or mitigate the potential impact of the user'sblood glucose level falling below a protection threshold value.Similarly, the infusion device may automatically transition from thesuspend delivery mode to another operating mode resume delivery of fluidto the user when both the current and predicted glucose values exceedtheir respective delivery resumption thresholds. In this regard, anydelivery (or dosage) commands determined in accordance with the normaldelivery control scheme are re-enabled or otherwise reactivated toresume regulating the user's blood glucose. For purposes of explanation,the subject matter may be described herein in the context of the normaldelivery control scheme (or delivery mode) that provides closed-loopcontrol of a physiological condition of the user (e.g., the user's bloodglucose) to regulate a current measurement value for the physiologicalcondition of the user to a target value. That said, it will beappreciated that the subject matter described herein can be implementedin an equivalent manner in embodiments where the normal delivery modecontrol scheme provides open-loop control to maintain a basal infusionrate of fluid to the user. Accordingly, the subject matter describedherein is not intended to any particular delivery mode or controlscheme.

In an exemplary embodiment, the threshold values used to suspend orresume delivery are based on a user-configurable protection thresholdvalue. For example, the user may input or otherwise provide a baselineblood glucose value below which the user would like to minimize his orher exposure to. For purposes of explanation, the input value from theuser is alternatively referred to herein as the suspend protectionthreshold (SPT) value or variants thereof. Based on the suspendprotection threshold value, a second threshold to be applied to thepredicted glucose value, alternatively referred to herein as apredictive suspend threshold value, may be calculated or otherwisedetermined, for example, by adding/subtracting an offset to/from thesuspend protection threshold value, multiplying the suspend protectionthreshold value by a conversion factor, or the like. In a similarmanner, a suspend enable threshold value to be applied to the currentglucose measurement value may also be calculated or determined based onthe suspend protection threshold value. In exemplary embodiments, theinfusion device is automatically transitioned to the suspend deliverymode when the predicted glucose value is less than or equal to thepredictive suspend threshold value and the user's current glucosemeasurement value is less than or equal to the suspend enable thresholdvalue, thereby reducing the likelihood of the user's current glucosemeasurement value reaching the suspend protection threshold value.Additionally, the infusion device may be automatically transitioned tothe suspend delivery mode when the user's current glucose measurementvalue is less than both the suspend protection threshold value and thesuspend enable threshold value. In this manner, suspension of deliveryis ensured when the current glucose measurement value reaches the levelfor which the user has indicated he or she would like protection.

In a similar manner, a resume (or delivery) enable threshold value thatis greater than or equal to the suspend protection threshold value maybe calculated or otherwise determined based on the suspend protectionthreshold value (e.g., by adding an offset). Additionally, a predictiveresume threshold value greater than the resume enable threshold valuemay be calculated or otherwise determined based on the suspendprotection threshold value and/or the resume enable threshold value(e.g., by adding another offset). Thereafter, when the user's currentglucose measurement value is greater than the resume enable thresholdvalue and the predicted glucose value is greater than the predictiveresume threshold value, the infusion device is automaticallytransitioned from the suspend delivery mode to an operating mode wheredelivery of fluid to the user is enabled. The resume delivery thresholdsmay be chosen relative to the suspend thresholds to provide a hystereticeffect. Additionally, in exemplary embodiments, a minimum suspensiontime period is imposed after transitioning to the suspend delivery modeto further ensure that the infusion device does not toggle betweenoperating modes. In exemplary embodiments, a refractory period is alsoimposed when transitioning from the suspend delivery mode to a deliverymode ensure that the infusion device does not repeatedly operate in thesuspend delivery mode without at least some recovery time periodelapsing.

During prolonged periods of nondelivery, the amount of the fluid thatremains active within the user's body (e.g., the fluid yet to bemetabolized or in the process of being metabolized) may become depleted.Furthermore, when fluid delivery is resumed, there may be a delaybetween when the fluid is infused and when the fluid begins having acorresponding effect on the physiological condition of the user, which,in turn, may result in the physiological condition reaching undesirablelevels. For example, infusion of insulin may be suspended when theuser's current and/or predicted blood glucose levels fall belowapplicable threshold values, as described above. While insulin infusionis suspended, the amount of active insulin in the user's body (i.e., theinsulin on board) decreases. Thereafter, as the user's blood glucoselevel rises, additional insulin may not be infused until the user'sblood glucose levels exceed a target blood glucose level. However, theuser's insulin response introduces a delay between the time when theinsulin is infused and the time when the corresponding response occursin the user's blood glucose, at which point, the user's blood glucoselevel may have risen to an undesirably high level.

As described in greater detail below in the context of FIGS. 20-21, inone or more embodiments, the infusion device may automaticallytransition from the suspend delivery mode to an alternative deliverymode that regulates an active amount of the fluid within the user'sbody, rather than maintaining a predetermined basal infusion rate orotherwise regulating the physiological condition of the user inaccordance with the normal delivery mode. For example, the infusiondevice may automatically transition from the suspend delivery mode to aninsulin on board (JOB) control mode that regulates the insulin infusionrate to maintain at least a threshold amount of insulin on board. Inthis regard, when the user's current glucose level is less than thedesired target (or reference) glucose level, the insulin on boardcontrol mode may provide a minimum infusion rate that may be greaterthan the infusion rate that would otherwise be determined based on thenormal closed-loop delivery mode based on the difference between theuser's current glucose measurement value and the user's target (orreference) glucose value. For example, even though the user's currentglucose measurement values and/or predicted glucose values may berising, the normal closed-loop delivery mode may result in a deliverycommand of zero (or nondelivery) while the user's current glucosemeasurement value is less than the user's target glucose value. Thus,the IOB control mode may preemptively infuse insulin to maintain theinsulin on board at a level that reduces the likelihood of ahyperglycemic rebound event in response to transitioning out of thesuspend delivery mode or another prolonged period of nondelivery.

In one or more embodiments, the IOB control mode may be utilized in lieuof or in addition to the suspend delivery mode. For example, when theuser's predicted blood glucose value and the user's current bloodglucose measurement value are both less than their applicable thresholdvalues for suspending delivery, the infusion device may automaticallytransition from a normal closed-loop delivery mode to the IOB controlmode to maintain at least a threshold amount of insulin on board. TheIOB control mode could be used in lieu of the suspend delivery mode.Thereafter, when the user's predicted blood glucose value and the user'scurrent blood glucose measurement value are both greater than theirapplicable threshold values for enabling the normal closed-loop deliverymode, the infusion device may automatically transition from the IOBcontrol mode back to the normal closed-loop delivery mode. Furthermore,in some embodiments, the infusion device may automatically transitionfrom the IOB control mode to the suspend delivery mode after previouslytransitioning from normal closed-loop delivery mode to the IOB controlmode, for example, when the user's current glucose measurement value isless than the absolute suspend protection threshold value set by theuser. Thus, the IOB control mode may be used instead of predictivelysuspending infusion delivery based on the predicted blood glucose value,while the suspend delivery mode is still utilized to automaticallysuspend delivery when the current blood glucose measurement value is ator below a mandatory suspend threshold value. In such embodiments, theIOB control mode may function as a buffer or transitional delivery modebetween the suspend delivery mode and the normal closed-loop oropen-loop delivery mode.

Turning now to FIG. 1, one exemplary embodiment of an infusion system100 includes, without limitation, a fluid infusion device (or infusionpump) 102, a sensing arrangement 104, a command control device (CCD)106, and a computer 108. The components of an infusion system 100 may berealized using different platforms, designs, and configurations, and theembodiment shown in FIG. 1 is not exhaustive or limiting. In practice,the infusion device 102 and the sensing arrangement 104 are secured atdesired locations on the body of a user (or patient), as illustrated inFIG. 1. In this regard, the locations at which the infusion device 102and the sensing arrangement 104 are secured to the body of the user inFIG. 1 are provided only as a representative, non-limiting, example. Theelements of the infusion system 100 may be similar to those described inU.S. patent application Ser. No. 13/049,803, the subject matter of whichis hereby incorporated by reference in its entirety.

In the illustrated embodiment of FIG. 1, the infusion device 102 isdesigned as a portable medical device suitable for infusing a fluid, aliquid, a gel, or other agent into the body of a user. In exemplaryembodiments, the infused fluid is insulin, although many other fluidsmay be administered through infusion such as, but not limited to, HIVdrugs, drugs to treat pulmonary hypertension, iron chelation drugs, painmedications, anti-cancer treatments, medications, vitamins, hormones, orthe like. In some embodiments, the fluid may include a nutritionalsupplement, a dye, a tracing medium, a saline medium, a hydrationmedium, or the like.

The sensing arrangement 104 generally represents the components of theinfusion system 100 configured to sense, detect, measure or otherwisequantify a condition of the user, and may include a sensor, a monitor,or the like, for providing data indicative of the condition that issensed, detected, measured or otherwise monitored by the sensingarrangement. In this regard, the sensing arrangement 104 may includeelectronics and enzymes reactive to a biological condition, such as ablood glucose level, or the like, of the user, and provide dataindicative of the blood glucose level to the infusion device 102, theCCD 106 and/or the computer 108. For example, the infusion device 102,the CCD 106 and/or the computer 108 may include a display for presentinginformation or data to the user based on the sensor data received fromthe sensing arrangement 104, such as, for example, a current glucoselevel of the user, a graph or chart of the user's glucose level versustime, device status indicators, alert messages, or the like. In otherembodiments, the infusion device 102, the CCD 106 and/or the computer108 may include electronics and software that are configured to analyzesensor data and operate the infusion device 102 to deliver fluid to thebody of the user based on the sensor data and/or preprogrammed deliveryroutines. Thus, in exemplary embodiments, one or more of the infusiondevice 102, the sensing arrangement 104, the CCD 106, and/or thecomputer 108 includes a transmitter, a receiver, and/or othertransceiver electronics that allow for communication with othercomponents of the infusion system 100, so that the sensing arrangement104 may transmit sensor data or monitor data to one or more of theinfusion device 102, the CCD 106 and/or the computer 108.

Still referring to FIG. 1, in various embodiments, the sensingarrangement 104 may be secured to the body of the user or embedded inthe body of the user at a location that is remote from the location atwhich the infusion device 102 is secured to the body of the user. Invarious other embodiments, the sensing arrangement 104 may beincorporated within the infusion device 102. In other embodiments, thesensing arrangement 104 may be separate and apart from the infusiondevice 102, and may be, for example, part of the CCD 106. In suchembodiments, the sensing arrangement 104 may be configured to receive abiological sample, analyte, or the like, to measure a condition of theuser.

As described above, in some embodiments, the CCD 106 and/or the computer108 may include electronics and other components configured to performprocessing, delivery routine storage, and to control the infusion device102 in a manner that is influenced by sensor data measured by and/orreceived from the sensing arrangement 104. By including controlfunctions in the CCD 106 and/or the computer 108, the infusion device102 may be made with more simplified electronics. However, in otherembodiments, the infusion device 102 may include all control functions,and may operate without the CCD 106 and/or the computer 108. In variousembodiments, the CCD 106 may be a portable electronic device. Inaddition, in various embodiments, the infusion device 102 and/or thesensing arrangement 104 may be configured to transmit data to the CCD106 and/or the computer 108 for display or processing of the data by theCCD 106 and/or the computer 108.

In some embodiments, the CCD 106 and/or the computer 108 may provideinformation to the user that facilitates the user's subsequent use ofthe infusion device 102. For example, the CCD 106 may provideinformation to the user to allow the user to determine the rate or doseof medication to be administered into the user's body. In otherembodiments, the CCD 106 may provide information to the infusion device102 to autonomously control the rate or dose of medication administeredinto the body of the user. In some embodiments, the sensing arrangement104 may be integrated into the CCD 106. Such embodiments may allow theuser to monitor a condition by providing, for example, a sample of hisor her blood to the sensing arrangement 104 to assess his or hercondition. In some embodiments, the sensing arrangement 104 and the CCD106 may be used for determining glucose levels in the blood and/or bodyfluids of the user without the use of, or necessity of, a wire or cableconnection between the infusion device 102 and the sensing arrangement104 and/or the CCD 106.

In some embodiments, the sensing arrangement 104 and/or the infusiondevice 102 are cooperatively configured to utilize a closed-loop systemfor delivering fluid to the user. Examples of sensing devices and/orinfusion pumps utilizing closed-loop systems may be found at, but arenot limited to, the following U.S. Pat. Nos. 6,088,608, 6,119,028,6,589,229, 6,740,072, 6,827,702, 7,323,142, and 7,402, 153, all of whichare incorporated herein by reference in their entirety. In suchembodiments, the sensing arrangement 104 is configured to sense ormeasure a condition of the user, such as, blood glucose level or thelike. The infusion device 102 is configured to deliver fluid in responseto the condition sensed by the sensing arrangement 104. In turn, thesensing arrangement 104 continues to sense or otherwise quantify acurrent condition of the user, thereby allowing the infusion device 102to deliver fluid continuously in response to the condition currently (ormost recently) sensed by the sensing arrangement 104 indefinitely. Insome embodiments, the sensing arrangement 104 and/or the infusion device102 may be configured to utilize the closed-loop system only for aportion of the day, for example only when the user is asleep or awake.

As described in greater detail below in the context of FIGS. 5-10, inexemplary embodiments, the sensing arrangement 104 and/or the infusiondevice 102 are cooperatively configured to determine one or morepredicted values for the condition in the body of the user at one ormore times in the future. Thereafter, the delivery of the fluid may beinfluenced by the one or more predicted values indicative of theanticipated future condition of the user in addition to a recentlyobtained value indicative of the current condition of the user. Forexample, commands for operating the infusion device to deliver insulinmay be determined as a function of a currently sensed blood glucosevalue and one or more predicted blood glucose values in a manner thataccounts for the anticipated response time for the insulin and/or theuser using the preceding blood glucose measurement values and/or thepreceding dosage commands. To put it another way, the control of auser's blood glucose level to regulate the user's blood glucose levelusing the user's current blood glucose level may be influenced by one ormore predicted blood glucose levels for the user in the future. Asdescribed in the context of FIGS. 11-19, in one or more exemplaryembodiments, the operating mode for the infusion device 102 isautomatically adjusted or altered based on the predicted blood glucosevalue and/or the current blood glucose measurement value violatingapplicable threshold values.

FIGS. 2-4 depict one exemplary embodiment of a fluid infusion device 200(or alternatively, infusion pump) suitable for use in an infusionsystem, such as, for example, as infusion device 102 in the infusionsystem 100 of FIG. 1. The fluid infusion device 200 is a portablemedical device designed to be carried or worn by a patient (or user),and the fluid infusion device 200 may leverage any number ofconventional features, components, elements, and characteristics ofexisting fluid infusion devices, such as, for example, some of thefeatures, components, elements, and/or characteristics described in U.S.Pat. Nos. 6,485,465 and 7,621,893. It should be appreciated that FIGS.2-4 depict some aspects of the infusion device 200 in a simplifiedmanner; in practice, the infusion device 200 could include additionalelements, features, or components that are not shown or described indetail herein.

As best illustrated in FIGS. 2-3, the illustrated embodiment of thefluid infusion device 200 includes a housing 202 adapted to receive afluid-containing reservoir 205. An opening 220 in the housing 202accommodates a fitting 223 (or cap) for the reservoir 205, with thefitting 223 being configured to mate or otherwise interface with tubing221 of an infusion set 225 that provides a fluid path to/from the bodyof the user. In this manner, fluid communication from the interior ofthe reservoir 205 to the user is established via the tubing 221. Theillustrated fluid infusion device 200 includes a human-machine interface(HMI) 230 (or user interface) that includes elements 232, 234 that canbe manipulated by the user to administer a bolus of fluid (e.g.,insulin), to change therapy settings, to change user preferences, toselect display features, and the like. The infusion device also includesa display element 226, such as a liquid crystal display (LCD) or anothersuitable display element, that can be used to present various types ofinformation or data to the user, such as, without limitation: thecurrent glucose level of the patient; the time; a graph or chart of thepatient's glucose level versus time; device status indicators; etc.

The housing 202 is formed from a substantially rigid material having ahollow interior 214 adapted to allow an electronics assembly 204, asliding member (or slide) 206, a drive system 208, a sensor assembly210, and a drive system capping member 212 to be disposed therein inaddition to the reservoir 205, with the contents of the housing 202being enclosed by a housing capping member 216. The opening 220, theslide 206, and the drive system 208 are coaxially aligned in an axialdirection (indicated by arrow 218), whereby the drive system 208facilitates linear displacement of the slide 206 in the axial direction218 to dispense fluid from the reservoir 205 (after the reservoir 205has been inserted into opening 220), with the sensor assembly 210 beingconfigured to measure axial forces (e.g., forces aligned with the axialdirection 218) exerted on the sensor assembly 210 responsive tooperating the drive system 208 to displace the slide 206. In variousembodiments, the sensor assembly 210 may be utilized to detect one ormore of the following: an occlusion in a fluid path that slows,prevents, or otherwise degrades fluid delivery from the reservoir 205 toa user's body; when the reservoir 205 is empty; when the slide 206 isproperly seated with the reservoir 205; when a fluid dose has beendelivered; when the infusion pump 200 is subjected to shock orvibration; when the infusion pump 200 requires maintenance.

Depending on the embodiment, the fluid-containing reservoir 205 may berealized as a syringe, a vial, a cartridge, a bag, or the like. Incertain embodiments, the infused fluid is insulin, although many otherfluids may be administered through infusion such as, but not limited to,HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs,pain medications, anti-cancer treatments, medications, vitamins,hormones, or the like. As best illustrated in FIGS. 3-4, the reservoir205 typically includes a reservoir barrel 219 that contains the fluidand is concentrically and/or coaxially aligned with the slide 206 (e.g.,in the axial direction 218) when the reservoir 205 is inserted into theinfusion pump 200. The end of the reservoir 205 proximate the opening220 may include or otherwise mate with the fitting 223, which securesthe reservoir 205 in the housing 202 and prevents displacement of thereservoir 205 in the axial direction 218 with respect to the housing 202after the reservoir 205 is inserted into the housing 202. As describedabove, the fitting 223 extends from (or through) the opening 220 of thehousing 202 and mates with tubing 221 to establish fluid communicationfrom the interior of the reservoir 205 (e.g., reservoir barrel 219) tothe user via the tubing 221 and infusion set 225. The opposing end ofthe reservoir 205 proximate the slide 206 includes a plunger 217 (orstopper) positioned to push fluid from inside the barrel 219 of thereservoir 205 along a fluid path through tubing 221 to a user. The slide206 is configured to mechanically couple or otherwise engage with theplunger 217, thereby becoming seated with the plunger 217 and/orreservoir 205. Fluid is forced from the reservoir 205 via tubing 221 asthe drive system 208 is operated to displace the slide 206 in the axialdirection 218 toward the opening 220 in the housing 202.

In the illustrated embodiment of FIGS. 3-4, the drive system 208includes a motor assembly 207 and a drive screw 209. The motor assembly207 includes a motor that is coupled to drive train components of thedrive system 208 that are configured to convert rotational motor motionto a translational displacement of the slide 206 in the axial direction218, and thereby engaging and displacing the plunger 217 of thereservoir 205 in the axial direction 218. In some embodiments, the motorassembly 207 may also be powered to translate the slide 206 in theopposing direction (e.g., the direction opposite direction 218) toretract and/or detach from the reservoir 205 to allow the reservoir 205to be replaced. In exemplary embodiments, the motor assembly 207includes a brushless DC (BLDC) motor having one or more permanentmagnets mounted, affixed, or otherwise disposed on its rotor. However,the subject matter described herein is not necessarily limited to usewith BLDC motors, and in alternative embodiments, the motor may berealized as a solenoid motor, an AC motor, a stepper motor, apiezoelectric caterpillar drive, a shape memory actuator drive, anelectrochemical gas cell, a thermally driven gas cell, a bimetallicactuator, or the like. The drive train components may comprise one ormore lead screws, cams, ratchets, jacks, pulleys, pawls, clamps, gears,nuts, slides, bearings, levers, beams, stoppers, plungers, sliders,brackets, guides, bearings, supports, bellows, caps, diaphragms, bags,heaters, or the like. In this regard, although the illustratedembodiment of the infusion pump utilizes a coaxially aligned drivetrain, the motor could be arranged in an offset or otherwise non-coaxialmanner, relative to the longitudinal axis of the reservoir 205.

As best shown in FIG. 4, the drive screw 209 mates with threads 402internal to the slide 206. When the motor assembly 207 is powered andoperated, the drive screw 209 rotates, and the slide 206 is forced totranslate in the axial direction 218. In an exemplary embodiment, theinfusion pump 200 includes a sleeve 211 to prevent the slide 206 fromrotating when the drive screw 209 of the drive system 208 rotates. Thus,rotation of the drive screw 209 causes the slide 206 to extend orretract relative to the drive motor assembly 207. When the fluidinfusion device is assembled and operational, the slide 206 contacts theplunger 217 to engage the reservoir 205 and control delivery of fluidfrom the infusion pump 200. In an exemplary embodiment, the shoulderportion 215 of the slide 206 contacts or otherwise engages the plunger217 to displace the plunger 217 in the axial direction 218. Inalternative embodiments, the slide 206 may include a threaded tip 213capable of being detachably engaged with internal threads 404 on theplunger 217 of the reservoir 205, as described in detail in U.S. Pat.Nos. 6,248,093 and 6,485,465, which are incorporated by referenceherein.

As illustrated in FIG. 3, the electronics assembly 204 includes controlelectronics 224 coupled to the display element 226, with the housing 202including a transparent window portion 228 that is aligned with thedisplay element 226 to allow the display 226 to be viewed by the userwhen the electronics assembly 204 is disposed within the interior 214 ofthe housing 202. The control electronics 224 generally represent thehardware, firmware, processing logic and/or software (or combinationsthereof) configured to control operation of the motor assembly 207and/or drive system 208, as described in greater detail below in thecontext of FIG. 5. Whether such functionality is implemented ashardware, firmware, a state machine, or software depends upon theparticular application and design constraints imposed on the embodiment.Those familiar with the concepts described here may implement suchfunctionality in a suitable manner for each particular application, butsuch implementation decisions should not be interpreted as beingrestrictive or limiting. In an exemplary embodiment, the controlelectronics 224 includes one or more programmable controllers that maybe programmed to control operation of the infusion pump 200.

The motor assembly 207 includes one or more electrical leads 236 adaptedto be electrically coupled to the electronics assembly 204 to establishcommunication between the control electronics 224 and the motor assembly207. In response to command signals from the control electronics 224that operate a motor driver (e.g., a power converter) to regulate theamount of power supplied to the motor from a power supply, the motoractuates the drive train components of the drive system 208 to displacethe slide 206 in the axial direction 218 to force fluid from thereservoir 205 along a fluid path (including tubing 221 and an infusionset), thereby administering doses of the fluid contained in thereservoir 205 into the user's body. Preferably, the power supply isrealized one or more batteries contained within the housing 202.Alternatively, the power supply may be a solar panel, capacitor, AC orDC power supplied through a power cord, or the like. In someembodiments, the control electronics 224 may operate the motor of themotor assembly 207 and/or drive system 208 in a stepwise manner,typically on an intermittent basis; to administer discrete precise dosesof the fluid to the user according to programmed delivery profiles.

Referring to FIGS. 2-4, as described above, the user interface 230includes HMI elements, such as buttons 232 and a directional pad 234,that are formed on a graphic keypad overlay 231 that overlies a keypadassembly 233, which includes features corresponding to the buttons 232,directional pad 234 or other user interface items indicated by thegraphic keypad overlay 231. When assembled, the keypad assembly 233 iscoupled to the control electronics 224, thereby allowing the HMIelements 232, 234 to be manipulated by the user to interact with thecontrol electronics 224 and control operation of the infusion pump 200,for example, to administer a bolus of insulin, to change therapysettings, to change user preferences, to select display features, to setor disable alarms and reminders, and the like. In this regard, thecontrol electronics 224 maintains and/or provides information to thedisplay 226 regarding program parameters, delivery profiles, pumpoperation, alarms, warnings, statuses, or the like, which may beadjusted using the HMI elements 232, 234. In various embodiments, theHMI elements 232, 234 may be realized as physical objects (e.g.,buttons, knobs, joysticks, and the like) or virtual objects (e.g., usingtouch-sensing and/or proximity-sensing technologies). For example, insome embodiments, the display 226 may be realized as a touch screen ortouch-sensitive display, and in such embodiments, the features and/orfunctionality of the HMI elements 232, 234 may be integrated into thedisplay 226 and the HMI 230 may not be present. In some embodiments, theelectronics assembly 204 may also include alert generating elementscoupled to the control electronics 224 and suitably configured togenerate one or more types of feedback, such as, without limitation:audible feedback; visual feedback; haptic (physical) feedback; or thelike.

Referring to FIGS. 3-4, in accordance with one or more embodiments, thesensor assembly 210 includes a back plate structure 250 and a loadingelement 260. The loading element 260 is disposed between the cappingmember 212 and a beam structure 270 that includes one or more beamshaving sensing elements disposed thereon that are influenced bycompressive force applied to the sensor assembly 210 that deflects theone or more beams, as described in greater detail in U.S. patentapplication Ser. No. 12/908,807, which is incorporated by referenceherein. In exemplary embodiments, the back plate structure 250 isaffixed, adhered, mounted, or otherwise mechanically coupled to thebottom surface 238 of the drive system 208 such that the back platestructure 250 resides between the bottom surface 238 of the drive system208 and the housing cap 216. The drive system capping member 212 iscontoured to accommodate and conform to the bottom of the sensorassembly 210 and the drive system 208. The drive system capping member212 may be affixed to the interior of the housing 202 to preventdisplacement of the sensor assembly 210 in the direction opposite thedirection of force provided by the drive system 208 (e.g., the directionopposite direction 218). Thus, the sensor assembly 210 is positionedbetween the motor assembly 207 and secured by the capping member 212,which prevents displacement of the sensor assembly 210 in a downwarddirection opposite the direction of arrow 218, such that the sensorassembly 210 is subjected to a reactionary compressive force when thedrive system 208 and/or motor assembly 207 is operated to displace theslide 206 in the axial direction 218 in opposition to the fluid pressurein the reservoir 205. Under normal operating conditions, the compressiveforce applied to the sensor assembly 210 is correlated with the fluidpressure in the reservoir 205. As shown, electrical leads 240 areadapted to electrically couple the sensing elements of the sensorassembly 210 to the electronics assembly 204 to establish communicationto the control electronics 224, wherein the control electronics 224 areconfigured to measure, receive, or otherwise obtain electrical signalsfrom the sensing elements of the sensor assembly 210 that are indicativeof the force applied by the drive system 208 in the axial direction 218.

FIG. 5 depicts an exemplary embodiment of a control system 500 suitablefor use with an infusion device 502, such as the infusion device 102 inFIG. 1 or the infusion device 200 of FIG. 2. The control system 500 isconfigured to control or otherwise regulate a condition in the body 501of a user to a desired (or target) value or otherwise maintain thecondition within a range of acceptable values. In one or more exemplaryembodiments, the condition being regulated is sensed, detected, measuredor otherwise quantified by a sensing arrangement 504 (e.g., sensingarrangement 104) communicatively coupled to the infusion device 502.However, it should be noted that in alternative embodiments, thecondition being regulated by the control system 500 may be correlativeto the measured values obtained by the sensing arrangement 504. Forexample, the condition being regulated could be a blood glucose level oranother condition that is influenced by physical activity of the user,and the sensing arrangement 504 may be realized as a heart rate monitor,a gyroscope, an accelerometer, or another suitable physiological sensorthat provides measured values indicative of the level of physicalactivity being exhibited by the user.

It should be appreciated that FIG. 5 is a simplified representation ofthe infusion device 502 for purposes of explanation and is not intendedto limit the subject matter described herein in any way. In this regard,more complex control schemes may be implemented by the control system500 with multiple sensing arrangements 504 being utilized in conjunctionwith one another. For example, a blood glucose sensing device may beused with a heart rate monitor to implement a control scheme thatregulates a user's blood glucose level based on the measured bloodglucose level in a manner that accounts for the user's level of physicalactivity. That said, for clarity and ease of explanation, the subjectmatter may be described herein in the context of the control system 500having an individual sensing arrangement 504 that senses, detects,measures or otherwise quantifies the condition being regulated.

In the illustrated embodiment, the infusion device 502 includes a motorcontrol module 512 coupled to a motor 507 (e.g., motor assembly 207)that is operable to displace a plunger 517 (e.g., plunger 217) in areservoir (e.g., reservoir 205) and provide a desired amount of fluid tothe body 501 of a user. In this regard, displacement of the plunger 517results in the delivery of a fluid that is capable of influencing thecondition in the body 501 of the user to the body 501 of the user via afluid delivery path (e.g., via tubing 221 of an infusion set 225). Amotor driver module 514 is coupled between an energy source 503 and themotor 507. The motor control module 512 is coupled to the motor drivermodule 514, and the motor control module 512 generates or otherwiseprovides command signals that operate the motor driver module 514 toprovide current (or power) from the energy source 503 to the motor 507to displace the plunger 517 in response to receiving, from a pumpcontrol system 520, a dosage command indicative of the desired amount offluid to be delivered. In this regard, the pump control system 520generally represents the electronics and other components that controloperation of the fluid infusion device 502 according to a desiredinfusion delivery program in a manner that is influenced by sensor datapertaining to a condition of a user (e.g., the user's current glucoselevel) received from the sensing arrangement 504 and/or in a manner thatis dictated by the user. To support closed-loop control, the pumpcontrol system 520 receives or otherwise obtains a desired value (e.g.,a target or command blood glucose value) for the condition in the body501 of the user. For example, the infusion device 502 may store orotherwise maintain the target value in a data storage element accessibleto the pump control system 520. Alternatively, the target value may bereceived from an external component (e.g., CCD 106 and/or computer 108).

In exemplary embodiments, the energy source 503 is realized as a batteryhoused within the infusion device 502 (e.g., within housing 202) thatprovides direct current (DC) power. In this regard, the motor drivermodule 514 generally represents the combination of circuitry, hardwareand/or other electrical components configured to convert or otherwisetransfer DC power provided by the energy source 503 into alternatingelectrical signals applied to respective phases of the stator windingsof the motor 507 that result in current flowing through the statorwindings that generates a stator magnetic field and causes the rotor ofthe motor 507 to rotate. The motor control module 512 is configured toreceive or otherwise obtain a commanded dosage from the pump controlsystem 520, convert the commanded dosage to a commanded translationaldisplacement of the plunger 517, and command, signal, or otherwiseoperate the motor driver module 514 to cause the rotor of the motor 507to rotate by an amount that produces the commanded translationaldisplacement of the plunger 517. For example, the motor control module512 may determine an amount of rotation of the rotor required to producetranslational displacement of the plunger 517 that achieves thecommanded dosage received from the pump control system 520. Based on thecurrent rotational position (or orientation) of the rotor with respectto the stator that is indicated by the output of the rotor sensingarrangement 516, the motor control module 512 determines the appropriatesequence of alternating electrical signals to be applied to therespective phases of the stator windings that should rotate the rotor bythe determined amount of rotation from its current position (ororientation). In embodiments where the motor 507 is realized as a BLDCmotor, the alternating electrical signals commutate the respectivephases of the stator windings at the appropriate orientation of therotor magnetic poles with respect to the stator and in the appropriateorder to provide a rotating stator magnetic field that rotates the rotorin the desired direction. Thereafter, the motor control module 512operates the motor driver module 514 to apply the determined alternatingelectrical signals (e.g., the command signals) to the stator windings ofthe motor 507 to achieve the desired delivery of fluid to the user.

When the motor control module 512 is operating the motor driver module514, current flows from the energy source 503 through the statorwindings of the motor 507 to produce a stator magnetic field thatinteracts with the rotor magnetic field. In some embodiments, after themotor control module 512 operates the motor driver module 514 and/ormotor 507 to achieve the commanded dosage, the motor control module 512ceases operating the motor driver module 514 and/or motor 507 until asubsequent dosage command is received. In this regard, the motor drivermodule 514 and the motor 507 enter an idle state during which the motordriver module 514 effectively disconnects or isolates the statorwindings of the motor 507 from the energy source 503. In other words,current does not flow from the energy source 503 through the statorwindings of the motor 507 when the motor 507 is idle, and thus, themotor 507 does not consume power from the energy source 503 in the idlestate, thereby improving efficiency.

Depending on the embodiment, the motor control module 512 may beimplemented or realized with a general purpose processor, amicroprocessor, a controller, a microcontroller, a state machine, acontent addressable memory, an application specific integrated circuit,a field programmable gate array, any suitable programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof, designed to perform the functions described herein.Furthermore, the steps of a method or algorithm described in connectionwith the embodiments disclosed herein may be embodied directly inhardware, in firmware, in a software module executed by the motorcontrol module 512, or in any practical combination thereof. Inexemplary embodiments, the motor control module 512 includes orotherwise accesses a data storage element or memory, including any sortof random access memory (RAM), read only memory (ROM), flash memory,registers, hard disks, removable disks, magnetic or optical massstorage, or any other short or long term storage media or othernon-transitory computer-readable medium, which is capable of storingprogramming instructions for execution by the motor control module 512.The computer-executable programming instructions, when read and executedby the motor control module 512, cause the motor control module 512 toperform the tasks, operations, functions, and processes describedherein.

As described in greater detail below in the context of FIGS. 6-10, inone or more embodiments, the pump control system 520 generates orotherwise determines the dosage commands for operating the motor 507 todisplace the plunger 517 based at least in part on a measurement valueindicative of the current condition in the body 501 of the user in amanner that is influenced by a predicted value for the condition. Inthis regard, the predicted value is calculated based at least in part onthe most recent (or current) measurement value and represents anestimate of the anticipated condition in the body 501 of the user at aparticular point of time in the future. In exemplary embodiments, thepump control system 520 may adjust or override the dosage command forregulating the condition of the user based on the predicted value. Forexample, the pump control system 520 may suspend fluid delivery (e.g.,by disabling the dosage command or setting the dosage command to zero)when the predicted value falls below a suspend delivery threshold valueand resume fluid delivery (e.g., by enabling the dosage command ordetermining a nonzero dosage command using the current measurementvalue) when the predicted value exceeds a resume delivery thresholdvalue. In exemplary embodiments, the resume delivery threshold value isdifferent from the suspend delivery threshold value. For example, theresume delivery threshold value may be equal to the suspend deliveryvalue plus some offset value (which may be a percentage of the suspenddelivery value). In other embodiments, the resume delivery thresholdvalue may be equal to the suspend delivery threshold value.

In accordance with one or more embodiments, based on the predictedvalue, the pump control system 520 may adjust the dosage command forregulating the condition of the user based on the observed condition ofthe user and the trends in the user's condition. For example, if apredicted blood glucose level indicates that the user's blood glucoselevel is expected to fall below a lower threshold value, the pumpcontrol system 520 may reduce the dosage command (e.g., to zero or someother relatively smaller amount) to ensure the blood glucose level ismaintained above the lower threshold value, even though the currentblood glucose measurement value indicates the blood glucose level issufficiently above the lower threshold value. Conversely, if thepredicted blood glucose level indicates that the user's blood glucoselevel is expected to exceed an upper threshold value, the pump controlsystem 520 may increase the dosage command to ensure the blood glucoselevel is maintained below the upper threshold value, even though thecurrent blood glucose measurement value indicates the blood glucoselevel is sufficiently below the upper threshold value. For example, if atarget blood glucose level is between a resume delivery threshold valueand a suspend delivery threshold value, the pump control system 520 maydecrease and/or increase the dosage command to attempt to maintain theblood glucose level between the resume delivery threshold value and thesuspend delivery threshold value, and thereby improve the likelihood ofthe blood glucose level being maintained at or near the target value.

In some embodiments, the pump control system 520 may generate orotherwise provide an alert based on the predicted value. For example,the pump control system 520 may generate or otherwise provide anauditory and/or visual notification to the user associated with theinfusion device 502 that fluid delivery can or should be suspended whenthe predicted value falls below a threshold value and/or that fluiddelivery can or should be resumed.

In exemplary embodiments, the predicted value is calculated by addingthe current measurement value to a weighted sum determined using thepreceding measurement values. In this regard, a sequence of the mostrecently obtained measurement values for the condition in the body 501of the user is stored or otherwise maintained. For example, in oneembodiment, the predicted value is calculated using a truncated Taylorseries expansion or a recursive prediction algorithm, such as aHolt-Winters exponential smoothing function. In some embodiments, thesensing arrangement 504 includes a data storage element (or memory) forstoring the sensor data sequence comprised of the current measurementvalue and a number of preceding measurement values, as described ingreater detail below in the context of FIG. 6. Additionally, in suchembodiments, the sensing arrangement 504 may calculate or otherwisedetermine the predicted value for the condition in the body 501 of theuser based on the stored sensor measurement data sequence and transmitor otherwise provide the predicted value to the pump control system 520along with the current measurement value. Alternatively, the sensingarrangement 504 may transmit or otherwise provide the sensor measurementdata sequence to the pump control system 520, which, in turn, calculatesthe predicted value using the sensor data sequence received from thesensing arrangement 504. In yet other embodiments, the pump controlsystem 520 may maintain a sensor measurement data sequence comprised ofthe current measurement value and a number of preceding measurementvalues received from the sensing arrangement 504 (e.g., by queuing orbuffering the most recently received current measurement values), andbased on the stored sensor measurement data sequence and the currentmeasurement value received from the sensing arrangement 504, the pumpcontrol system 520 determines the predicted value for the condition inthe body 501 of the user, as described in the context of FIG. 7.

As described in the context of FIGS. 8-10, in exemplary embodiments,either the sensing arrangement 504 or the pump control system 520analyzes or otherwise monitors the sensor measurement data sequenceand/or the current measurement value to detect or otherwise identifywhen one or more measurement values in the sequence are invalid,unreliable, unacceptable, or otherwise unusable. In this regard, ameasurement value is unusable when one or more characteristics of themeasurement value is indicative of the measurement value beingcorrupted, unreliable, or otherwise unacceptable for purposes ofdetermining a predicted value based thereon. In response to detecting anunusable measurement value in a sensor measurement data sequence, thesensing arrangement 504 and/or the pump control system 520 modifies thesensor measurement data sequence to ameliorate the invalid measurementvalue, for example, by interpolating that value in the measurementsequence using acceptable measurement values that precede and succeedthe unusable measurement or replacing the unusable measurement value inthe sequence with a value of a succeeding measurement value in thesequence. In this manner, by virtue of modifying the sensor measurementdata sequence and calculating the predicted value in a deterministicmanner, a relatively reliable predicted value may be determined andutilized without having to reset the prediction calculation (e.g.,deleting or discarding the measurement sequence) and/or incur theadditional lag time associated with resetting the prediction calculationand/or waiting for a complete sequence of usable values to be obtained(e.g., the time required for the data sequence to be filled with theusable measurement values).

Again, it should be understood that FIG. 5 depicts a simplifiedrepresentation of the infusion device 502 for purposes of explanationand is not intended to limit the subject matter described herein in anyway. In this regard, depending on the embodiment, some features and/orfunctionality of the sensing arrangement 504 may implemented by orotherwise integrated into the pump control system 520, or vice versa.Similarly, in practice, the features and/or functionality of the motorcontrol module 512 may implemented by or otherwise integrated into thepump control system 520, or vice versa. Furthermore, the features and/orfunctionality of the pump control system 520 may be implemented bycontrol electronics 224 located in the fluid infusion device 200, 400,while in alternative embodiments, the pump control system 520 may beimplemented by a remote computing device that is physically distinctand/or separate from the infusion device 502, such as, for example, theCCD 106 or the computer 108. Additionally, although FIG. 5 depicts thesensing arrangement 504 as being physically separate and distinct fromthe infusion device 502, in alternative embodiments, the sensingarrangement 504 may be integrated into or otherwise implemented by theinfusion device 502 (e.g., by providing the sensing arrangement 504within the housing 202).

FIG. 6 depicts an exemplary embodiment of a sensing arrangement 600suitable for use as the sensing arrangement 504 in FIG. 5 in accordancewith one or more embodiments. The illustrated sensing arrangement 600includes, without limitation, a control module 602, a sensing element604, a communications interface 606, and a data storage element (ormemory) 608. The control module 602 is coupled to the sensing element604, the communications interface 606, and the memory 608, and thecontrol module 602 is suitably configured to support the operations,tasks, and/or processes described herein.

The sensing element 604 generally represents the component of thesensing arrangement 600 that are configured to generate, produce, orotherwise output one or more electrical signals indicative of acharacteristic that is sensed, measured, or otherwise quantified by thesensing arrangement. In this regard, a characteristic of the outputelectrical signal provided by the sensing element 604 corresponds or isotherwise correlative to the characteristic that the sensing element 604senses, detects, measures, or otherwise quantifies. For example,referring to FIG. 5, the sensing element 604 may be realized as aglucose sensing element that generates an electrical signal, wherein acurrent (or voltage) associated with the electrical signal iscorrelative to the blood glucose level that is sensed or otherwisemeasured in the body 501 of the user.

Still referring to FIG. 6, the control module 602 generally representsthe hardware, circuitry, logic, firmware and/or other component of thesensing arrangement 600 that is coupled to the sensing element 604, andthe control module 602 is configured to receive the measurement datafrom the sensing element 604 and perform various additional tasks,operations, functions and/or operations described herein. For example,in one or more embodiments, the control module 602 implements orotherwise executes a data management application 610 that processes themeasurement data received from the sensing element 604 to detect orotherwise identify whether measurement data value received from thesensing element 604 is valid or otherwise acceptable, and when ameasurement data value is unacceptable, the data management application610 substitutes a modified measurement data value for the unacceptablemeasurement data value in a data sequence of the most recent measurementdata values. Additionally, in one or more embodiments, the controlmodule 602 also implements or otherwise executes a data predictionapplication 612 that calculates or otherwise determines one or morepredicted values for the characteristic sensed by the sensing element604 based on the sequence of the most recent measurement data valuesreceived from the data management application 610. In this regard, apredicted value for the sensed characteristic at a time in the futuremay be influenced by or otherwise based at least in part on the modifiedmeasurement data value substituted by the data management application610 in lieu of the unacceptable measurement data value received from thesensing element 604, as described in greater detail below.

Depending on the embodiment, the control module 602 may be implementedor realized with a general purpose processor, a microprocessor, acontroller, a microcontroller, a state machine, a content addressablememory, an application specific integrated circuit, a field programmablegate array, any suitable programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof, designed to perform the functions described herein. In thisregard, the steps of a method or algorithm described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in firmware, in a software module executed by the control module 602, orin any practical combination thereof. In some embodiments, the controlmodule 602 includes an analog-to-digital converter (ADC) or anothersimilar sampling arrangement that converts the output data signalreceived from the sensing element 604 into corresponding digitalmeasurement data value. For example, the control module 602 may convertan output electrical signal received from the sensing element 604 intocorresponding digital measurement value (e.g., an uncalibrated glucosesensor electrical current value).

In exemplary embodiments, the control module 602 includes or otherwiseaccesses the data storage element or memory 608. The memory 608 may berealized using any sort of RAM, ROM, flash memory, registers, harddisks, removable disks, magnetic or optical mass storage, short or longterm storage media, or any other non-transitory computer-readable mediumcapable of storing programming instructions for execution by the controlmodule 602. The computer-executable programming instructions, when readand executed by the control module 602, cause the control module 602 toimplement or otherwise generate the applications 610, 612 and performthe tasks, operations, functions, and processes described in greaterdetail below.

The communications interface 606 generally represents the hardware,circuitry, logic, firmware and/or other components of the sensingarrangement 600 that are coupled to the control module 602 andconfigured to support communications to/from the sensing arrangement600. The communications interface 606 may include or otherwise becoupled to one or more transceiver modules capable of supportingwireless communications between the sensing arrangement 600 and anotherelectronic device (e.g., an infusion device 102, 502 or anotherelectronic device 106, 108 in an infusion system 100). Alternatively,the communications interface 606 may be realized as a port that isadapted to receive or otherwise be coupled to a wireless adapter thatincludes one or more transceiver modules and/or other components thatsupport the operations of the sensing arrangement 600 described herein.In other embodiments, the communications interface 606 may be configuredto support wired communications to/from the sensing arrangement 600.

It should be understood that FIG. 6 is a simplified representation of asensing arrangement 600 for purposes of explanation and is not intendedto limit the subject matter described herein in any way. In this regard,although FIG. 6 depicts the various elements residing within the sensingarrangement 600, one or more elements of the sensing arrangement 600 maybe distinct or otherwise separate from the other elements of the sensingarrangement 600. For example, the sensing element 604 may be separateand/or physically distinct from the control module 602 and/or thecommunications interface 606. Furthermore, although FIG. 6 depicts thedata management application 610 and the data prediction application 612as being implemented by the sensing arrangement 600, in alternativeembodiments, features and/or functionality of the data managementapplication 610 and/or the data prediction application 612 may beimplemented by or otherwise reside on the infusion device 102, 502 oranother device 106, 108 within an infusion system 100. For example, asdescribed in greater detail below, in some embodiments, the datamanagement application 610 implemented by the sensing arrangement 600may merely detect or otherwise identify unacceptable measurement datavalues and provide a corresponding notification of the unacceptablemeasurement data value to the infusion device 102, 502, which, in turn,substitutes a modified measurement data value for the unacceptablemeasurement data value and determines one or more predicted values forthe sensed characteristic based thereon.

FIG. 7 depicts an exemplary embodiment of a pump control system 700suitable for use as the pump control system 520 in FIG. 5 in accordancewith one or more embodiments. The illustrated pump control system 700includes, without limitation, a pump control module 702, acommunications interface 704, and a data storage element (or memory)706. The pump control module 702 is coupled to the communicationsinterface 704 and the memory 706, and the pump control module 702 issuitably configured to support the operations, tasks, and/or processesdescribed herein.

Referring to FIG. 7 and with reference to FIG. 5, the communicationsinterface 704 generally represents the hardware, circuitry, logic,firmware and/or other components of the pump control system 700 that arecoupled to the pump control module 702 and configured to supportcommunications between the pump control system 700 and the sensingarrangement 504. In this regard, the communications interface 704 mayinclude or otherwise be coupled to one or more transceiver modulescapable of supporting wireless communications between the pump controlsystem 520, 700 and the sensing arrangement 504 or another electronicdevice 106, 108 in an infusion system 100. In other embodiments, thecommunications interface 704 may be configured to support wiredcommunications to/from the sensing arrangement 504.

The pump control module 702 generally represents the hardware,circuitry, logic, firmware and/or other component of the pump controlsystem 700 that is coupled to the communications interface 704 andconfigured to determine dosage commands for operating the motor 507 todeliver fluid to the body 501 based on data received from the sensingarrangement 504 and perform various additional tasks, operations,functions and/or operations described herein. For example, in exemplaryembodiments, pump control module 702 implements or otherwise executes acommand generation application 714 that calculates or otherwisedetermines a dosage command for operating the motor 507 of the infusiondevice 502 based at least in part on a current measurement value for acondition in the body 501 of the user, a predicted measurement value forthat condition in the body 501 of the user, and one or more reference(or target) values for that condition in the body 501 of the user. Forexample, the command generation application 714 may determine a dosagecommand for operating the motor 507 to deliver insulin to the body 501of the user based at least in part on a current blood glucosemeasurement value, a predicted blood glucose measurement value at a timein the future (e.g., in 30 minutes from the current time), and areference glucose value. For example, the reference value may be equalto the threshold blood glucose value at which insulin delivery should besuspended, wherein the command generation application 714 sets thedosage command to zero to suspend operation of the motor 507 (andthereby, suspend delivery) when the current blood glucose measurementvalue is less than or equal to the threshold blood glucose value.Conversely, when the current blood glucose measurement value is greaterthan a threshold blood glucose value (e.g., the resume deliverythreshold), the command generation application 714 may determine anonzero dosage command for operating the motor 507 to deliver insulin tothe body 501 of the user based at least in part on the current bloodglucose measurement value. In the case of closed-loop control, thedosage command determined by the command generation application 714 maybe configured to regulate the user's blood glucose level to a targetblood glucose value.

Referring to FIG. 7 with reference to FIGS. 5-6, in some embodiments,the pump control module 702 may also implement or otherwise execute adata prediction application 712 and/or a data management application 710in lieu of and/or in addition to the applications 610, 612 beingimplemented by the sensing arrangement 504, 600. In this regard, in someembodiments, the sensing arrangement 504, 600 may merely transmit thecurrent measurement value and/or a sequence of recent measurementvalues, either with or without indications of whether those measurementvalues are valid and/or acceptable. In such embodiments, the datamanagement application 710 on the pump control module 702 may processthe measurement data received from the sensing arrangement 504, 600 todetect or otherwise identify whether any of the measurement data valuesreceived from the sensing arrangement 504, 600 are invalid or otherwiseunacceptable. In this regard, the data management application 710 mayalso detect or otherwise measurement data values that were dropped,lost, or otherwise failed to be received by the communications interface704. In a similar manner as described above, the data managementapplication 710 substitutes a modified measurement data value for anunacceptable measurement data value to provide a modified data sequencefor the most recent measurement data values. Similarly, in one or moreembodiments, the pump control module 702 may also implement or otherwiseexecute a data prediction application 712 that calculates or otherwisedetermines one or more predicted values for the characteristicquantified by the sensing arrangement 504, 600 based on the sequence ofthe most recent measurement data values provided by the data managementapplication 610. Thus, a predicted value for a sensed characteristic ata time in the future may be influenced by or otherwise based at least inpart on the modified data sequence provided by data managementapplication 710, as described in greater detail below.

Still referring to FIG. 7, depending on the embodiment, the controlmodule 702 may be implemented or realized with a general purposeprocessor, a microprocessor, a controller, a microcontroller, a statemachine, a content addressable memory, an application specificintegrated circuit, a field programmable gate array, any suitableprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof, designed to perform thefunctions described herein. In this regard, the steps of a method oralgorithm described in connection with the embodiments disclosed hereinmay be embodied directly in hardware, in firmware, in a software moduleexecuted by the control module 702, or in any practical combinationthereof. In exemplary embodiments, the pump control module 702 includesor otherwise accesses the data storage element or memory 708, which maybe realized using any sort of non-transitory computer-readable mediumcapable of storing programming instructions for execution by the pumpcontrol module 702. The computer-executable programming instructions,when read and executed by the control module 702, cause the controlmodule 702 to implement or otherwise generate one or more of theapplications 710, 712, 714 and perform the tasks, operations, functions,and processes described in greater detail below.

It should be understood that FIG. 7 is a simplified representation of apump control system 700 for purposes of explanation and is not intendedto limit the subject matter described herein in any way. For example, insome embodiments where the sensing arrangement 504, 600 implements thefeatures and/or functionality of the data management application 710and/or the data prediction application 712, such applications 710, 712may be absent from the pump control system 700. Furthermore, in someembodiments, the features and/or functionality of the motor controlmodule 512 may be implemented by or otherwise integrated into the pumpcontrol system 700 and/or the pump control module 702, for example, bythe command generation application 714 converting the dosage commandinto a corresponding motor command, in which case, the separate motorcontrol module 512 may be absent from an embodiment of the infusiondevice 502.

FIG. 8 depicts an exemplary control process 800 suitable forimplementation by a control system in a fluid infusion device, such asthe control system 500 in the infusion device 502, to determine commandsfor operating a motor to deliver fluid to a user in a manner that isinfluenced by one or more predicted measurement values for a conditionof the user at some point in the future. The various tasks performed inconnection with the control process 800 may be performed by hardware,firmware, software executed by processing circuitry, or any combinationthereof. For illustrative purposes, the following description refers toelements mentioned above in connection with FIGS. 1-7. In practice,portions of the control process 800 may be performed by differentelements of the control system 500, such as, for example, the infusiondevice 502, the sensing arrangement 504, 600, the pump control system520, 700, the motor control module 512, and/or the motor 507. It shouldbe appreciated that the control process 800 may include any number ofadditional or alternative tasks, the tasks need not be performed in theillustrated order and/or the tasks may be performed concurrently, and/orthe control process 800 may be incorporated into a more comprehensiveprocedure or process having additional functionality not described indetail herein. Moreover, one or more of the tasks shown and described inthe context of FIG. 8 could be omitted from a practical embodiment ofthe control process 800 as long as the intended overall functionalityremains intact.

In exemplary embodiments, the control process 800 initializes orotherwise begins by receiving or otherwise obtaining a new measurementdata value (or sample) for a condition in the body of a user andupdating a measurement data sequence of recent measurement data valuesfor the user to include the new measurement data value (task 802, 804).In this regard, the control module 602 may sample, poll, or otherwiseoperate the sensing element 604 to obtain a new sample of the level of acondition in the body 501 of the user. In exemplary embodiments, thecontrol module 602 obtains the new sample from the sensing element 604on a regular periodic basis. For example, the control module 602 maysample the output of the sensing element 604 every five minutes toobtain a new measurement of the blood glucose level in the body 501 ofthe user. After obtaining a new sample, the control module 602 mayobtain a stored sequence of recent measurement samples from the memory608, add the new sample to the sequence of recent measurement samples,and shift the precedence of the previous measurement samples to followthe new measurement sample in the updated measurement sequence. Forexample, the sequence of recent measurement samples may be realized as afirst-in first-out (FIFO) queue of measurement samples that are orderedsequentially, where the control module 602 updates the sequence ofrecent measurement samples by adding the measurement value for the newsample to the FIFO queue and removing the value of the oldestmeasurement sample from the queue. For purposes of explanation, the newor most measurement data value (or sample) may alternatively be referredto herein as the current measurement data value (or sample). In one ormore embodiments, after updating the measurement data sequence, the datamanagement application 610 stores or otherwise maintains the updatedmeasurement sequence in memory 608, for example, by overwriting thepreviously stored measurement sequence. In some embodiments, the memory608 may maintain the previously stored measurement sequence and thecurrent (or updated) measurement sequence in memory 608 to supportinterpolating unusable measurement values using acceptable measurementvalues from the preceding stored measurement sequence, as described ingreater detail below in the context of FIGS. 9-10.

Still referring to FIG. 8, the illustrated control process 800 continuesby determining whether the new measurement sample is usable, and inresponse to determining that the new measurement sample is unusable, thecontrol process 800 flags or otherwise indicates that the newmeasurement sample is unusable (tasks 806, 808). In this regard, whenimplemented by the sensing arrangement 504, 600, the data managementapplication 610 applies various validation criteria and/or logic to thenew measurement sample to verify that the new measurement sample issufficiently accurate and/or reliable before the new measurement sampleis capable of influencing operation of the infusion device 502. Forexample, the data management application 610 may ensure that the newmeasurement sample is greater than a minimum threshold value, less thana maximum threshold value, or otherwise within a range of acceptablevalid measurement values for the condition in the body 501 of the user.Similarly, the data management application 610 may calculate orotherwise obtain one or more characteristics associated with the newmeasurement sample and ensure an obtained characteristic is greater thana minimum threshold value, less than a maximum threshold value, orotherwise within a range of acceptable values for that characteristic ofthe new measurement sample. For example, the data management application610 may determine or obtain a signal-to-noise ratio associated with thenew measurement sample and compare the signal-to-noise ratio to aminimum acceptable signal-to-noise ratio to ensure that the measurementvalue is not likely to have been corrupted or overly influenced bynoise.

When the data management application 610 determines the new measurementsample is unusable (e.g., because its value is not within the range ofacceptable valid measurement values, its signal-to-noise ratio is toolow, or the like), the data management application 610 may flag orotherwise mark the new measurement sample as being invalid or otherwiseunusable so that the measurement value is not utilized when determiningcommands for operating the motor 507 of the infusion device 502. Forexample, in some embodiments, the data management application 610 mayreplace the measurement value with an error code. In other embodiments,the sequence of recent measurement samples may maintain, in associationwith each respective measurement sample in the sequence, an indicationof whether that respective measurement sample is acceptable or otherwiseusable for subsequently determining dosage commands.

In accordance with one or more embodiments, when the current measurementsample is unusable, the sensing arrangement 504, 600 also transmits orotherwise provides the current measurement value and/or the updatedmeasurement sample sequence to the infusion device 502 and/or the pumpcontrol system 520, 700 with a corresponding indication or notificationthat the current (or most recent) measurement is unacceptable. Forexample, the sensing arrangement 504, 600 may transmit or otherwiseprovide an error code for the current measurement sample or anotherindication that the current measurement sample is unusable or otherwiseunacceptable. In some embodiments, when the infusion device 502 and/orthe pump control system 520, 700 receives an error code for the currentmeasurement sample or another an indication that the current measurementsample is unusable or otherwise unacceptable, the pump control system520, 700 and/or the command generation application 714 may implement amodified control scheme or algorithm for determining dosage commandsindependent of any current and/or predicted measurement values in amanner that is likely to maintain the condition in the body 501 of theuser within an acceptable range. In accordance with one embodiment, whenthe delivery has been suspended and more than a threshold number ofunusable measurement samples have been received by the infusion device502 while delivery is suspended, the pump control system 520, 700 and/orthe command generation application 714 may automatically resumedelivery.

Still referring to FIG. 8, when the new measurement sample is acceptableand usable, the control process 800 continues by determining whether thesequence of recent measurement samples is valid or otherwise acceptablefor use in subsequently determining dosage commands for operating theinfusion device (task 810). In this regard, the data managementapplication 610 analyzes each measurement sample in the recentmeasurement sample sequence to ensure that none of the measurementsamples has been flagged or otherwise identified as being unusable. Whenall of the measurement samples in the recent measurement sample sequenceare usable, the control process 800 determines the measurement sequenceis valid and acceptable and proceeds with determining a predictedmeasurement value for the condition in the body of the user at a time inthe future and determining dosage commands for operating the infusiondevice in a manner that is influenced by the predicted measurement value(tasks 818, 820), in a similar manner as described below.

In exemplary embodiments, when the control process 800 determines thatthe sequence of recent measurement samples is invalid or otherwiseunacceptable, the control process 800 continues by determining whetherthe recent measurement sample sequence can be interpolated to substitutemodified measurement values for the measurement samples that have beenflagged or otherwise identified as being unusable (task 812). In thisregard, the data management application 610 determines whether thedifference between two sequential usable values is less than or equal toa threshold number of measurement samples. The threshold number ofmeasurement samples corresponds to a threshold amount of time that isshort enough in duration that interpolating the recent measurementsample sequence to replace the unusable measurement samples between twosequential acceptable values allows any predicted measurement valuescalculated based thereon to achieve a desired level of accuracy and/orreliability. For example, if it is determined that gaps betweensequential usable values that are less than or equal to 20 minutes canbe interpolated and still result in predicted measurement values havinga desired level of accuracy and/or reliability, then the thresholdnumber of measurement samples may be chosen to be the number ofmeasurement samples that would be expected to be obtained within a 20minute timeframe. Continuing the example described above, if the newmeasurement samples are obtained every 5 minutes, a threshold number ofmeasurement samples between sequential usable measurement values equalto 3 measurement samples will allow gaps of up to 20 minutes betweenusable measurement values to be interpolated. Thus, the data managementapplication 610 may interpolate between any two usable measurementsamples that are separated by three or fewer unusable measurementsamples to obtain a modified (or adjusted) recent measurement samplesequence that does not include any invalid and/or unusable measurementvalues.

If the unusable measurement sample(s) in the recent measurement samplesequence can be interpolated, the control process 800 continues byperforming interpolation using preceding and succeeding usablemeasurement samples in the measurement sequence to obtain one or moreinterpolated measurement values corresponding to one or more unusablemeasurement samples in the recent measurement sample sequence (task814). The recent measurement sample sequence is then modified orotherwise adjusted by substituting the interpolated measurement valuesfor the corresponding unusable measurement values, resulting in amodified (or adjusted) recent measurement sample sequence that does notinclude unusable measurement values for samples in the sequence thathave been identified as unusable. For example, the data managementapplication 610 may perform interpolation using any number of acceptablemeasurement samples that precede and/or succeed an unusable measurementsample (or consecutive unusable measurement samples) to determineinterpolated measurement values for the unusable measurement sample(s).In accordance with one embodiment, the data management application 610utilizes linear interpolation to obtain an interpolated measurementvalue for an unusable measurement sample(s) between two usablemeasurement samples. However, it should be appreciated that the subjectmatter described herein is not limited to any particular type ofinterpolation utilized to replace unusable measurement samples. In someembodiments, after modifying the measurement data sequence, the datamanagement application 610 may store or otherwise maintain the modifiedmeasurement sequence in memory 608. In other embodiments, the datamanagement application 610 may provide the modified measurement sequenceto the data prediction application 612 while storing or otherwisemaintaining the original unmodified measurement sequence in memory 608.

When the control process 800 determines recent measurement samplesequence cannot be interpolated, the control process 800 continues byreplacing unusable measurement samples in the recent measurement samplesequence with the value of a more recently obtained usable measurementvalue (task 816). In this regard, when the number of consecutiveunusable measurement samples exceeds a threshold number of measurementsamples that are allowed to be interpolated (alternatively referred toherein as the interpolatable threshold), those consecutive unusablemeasurement samples are replaced with the more recent measurement datavalue that succeeds or follows those unusable measurement samples in therecent measurement sample sequence. In other words, the data managementapplication 610 backfills consecutive unusable measurement samples thatexceed the interpolatable threshold with the more recent usablemeasurement data value that immediately follows those consecutiveunusable measurement samples. In some embodiments, any usablemeasurement samples that precede the consecutive unusable measurementsamples in the recent measurement sample sequence are also replaced orotherwise backfilled to eliminate any potential spike, jump or otherdiscontinuity at the transition from those prior usable measurementsamples to the current measurement sample value being backfilled. Forexample, continuing the example described above, if the interpolatablethreshold number of measurement samples is equal to 3 and the number ofconsecutive unusable measurement samples is greater than or equal to 4,the data management application 610 may replace the consecutive unusablemeasurement samples and any older measurement samples in the recentmeasurement sample sequence with the usable measurement value thatimmediately follows the consecutive unusable measurement samples in thesequence.

It should be noted that in some embodiments of the control process 800,both interpolation and replacement may be performed on a measurementdata sequence to obtain a modified measurement data sequence. Forexample, as described in greater detail below in the context of FIGS.9-10, in situations where there are multiple sets of consecutiveunusable measurement samples in the sequence, any set of consecutiveunusable measurement samples that has fewer than the interpolatablethreshold number may be interpolated while any set of consecutiveunusable measurement samples that has greater than the interpolatablethreshold number may be replaced with the immediately following usablemeasurement value.

Additionally, it should also be noted that in some embodiments of thecontrol process 800, when the measurement sequence is incomplete orotherwise does not contain the steady state number of measurementsamples, the control process 800 may determine that the measurementsequence is not valid and acceptable (e.g., because it does not containthe desired amount of usable measurement values), in which case thecontrol process 800 may proceed by backfilling the measurement sequenceusing the oldest usable measurement value in the measurement sequence.For example, the measurement sequence in memory 608 may initially bepopulated with an error code, a null value, or the like, therebyindicating the samples in the initial measurement sequence are notusable. If the measurement sequence contains 9 samples at steady stateand the current measurement sequence contains only 2 usable samples, thecontrol process 800 may backfill the measurement sequence with the leastrecent of the usable samples to obtain a complete modified measurementdata sequence with the steady state number of measurement sample values.In this regard, upon initialization of the control system 500, predictedvalues for the condition in the body 501 of the user may still becalculated. Furthermore, in yet other embodiments, a complete modifiedmeasurement data sequence may be obtained by extrapolating the usablemeasurement data values backwards to fill the measurement data sequence.

Still referring to FIG. 8, after obtaining a modified recent measurementsample sequence, the control process 800 continues by determining apredicted measurement value for the condition in the body of the user ata time in the future (task 818). In exemplary embodiments, the dataprediction application 612 calculates the predicted measurement valuebased at least in part on the current measurement data value and aweighted sum determined using the measurement data values in the recentmeasurement sample sequence received from the data managementapplication 610 and/or memory 608. Thus, when one or more previouslyunusable measurement samples have been modified, either by interpolationor replacement with a more recent value, the predicted measurement valueis calculated or otherwise determined based at least in part on thosemodified measurement data values in addition to the originallyacceptable measurement values maintained in the modified measurementsequence.

In one or more exemplary embodiments, a predicted blood glucose level inthe body 501 of the user at a time in the future is calculated using theequation ŷ=y_(t)+hb_(t), where ŷ is the predicted blood glucose level,y_(t) is equal to the current (or most recent) blood glucose measurementvalue, h is the prediction horizon in terms of number of measurementsamples in the future from the current time, and b_(t) is the estimateof the trend in the measurements that is determined as a weighted sum ofthe measurement values in the recent measurement sequence. In exemplaryembodiments, b_(t) is governed by the equation

${b_{t} = {\sum\limits_{k = 1}^{n}{{\beta\left( {1 - \beta} \right)}^{({k - 1})}b_{t - k}}}},$where β is a tuning parameter, n is equal to the number of older bloodglucose measurement values in the measurement sequence that precede thecurrent measurement value. The b_(t-k) term is calculated as thedifference between the k^(th) blood glucose measurement value precedingthe current measurement value in the measurement sequence and the bloodglucose measurement value that immediately precedes the k^(th) bloodglucose measurement value in the measurement sequence (e.g.,b_(t-k)=y_(t-k)−y_(t-k-1)). In this regard, t corresponds to the current(or most recent) measurement sampling time (e.g., y_(t) is the first ormost recent measurement sample in the sequence), t−1 corresponds to thepreceding (or next most recent) measurement sampling time (e.g., y_(t-1)is the second most recent measurement sample in the sequence), and soon, such that y_(t-n) corresponds to the oldest (or least recent)measurement sample in the sequence. It should be noted that the estimateof the trend is calculated in a deterministic manner rather than arecursive manner using a truncated Taylor series expansion of theequation b_(t)=β(y_(t)−y_(t-1))+(1−β)b_(t-1), which, in turn, allows theestimate of the trend to be calculated using a modified data sequence inthe event of unusable measurement samples rather than having toreinitialize the calculation. In one embodiment, the anticipated (orexpected) blood glucose level in the body 501 of the user 30 minutesinto the future. Thus, continuing the above example, if the measurementsamples are obtained every 5 minutes, the predicted blood glucose level30 minutes into the future (ŷ) is calculated by setting h=6, whichcorresponds to the number of measurement samples that would be obtainedover a 30 minute duration of time.

After determining a predicted measurement value, the control process 800continues by determining commands for operating the infusion device in amanner that is influenced by the predicted measurement value (task 820).For example, the sensing arrangement 504, 600 may transmit or otherwiseprovide the current blood glucose measurement value (y_(t)) and thepredicted blood glucose measurement value (ŷ) in the body 501 of theuser 30 minutes into the future to the pump control system 520, 700.Thereafter, the pump control system 520, 700 and/or command generationapplication 714 determines a dosage command based on the current bloodglucose measurement value and one or more target blood glucosemeasurement value in a manner that is influenced by or otherwiseaccounts for the predicted blood glucose measurement value. For example,the pump control system 520, 700 and/or command generation application714 may determine an initial dosage command based on a differencebetween the current blood glucose measurement value and a target bloodglucose measurement value, and then utilize the predicted blood glucosemeasurement value as a modification factor that increases and/ordecreases that dosage command, which is then provided to the motorcontrol module 512 for generating appropriate motor commands. In someembodiments, the pump control system 520, 700 and/or command generationapplication 714 may set the dosage command to zero when the predictedblood glucose value is less than a lower threshold blood glucose level.As described above in the context of FIG. 5, in response to receiving adosage command, the motor control module 512 may convert the dosagecommand to a corresponding motor command (e.g., a number of steps ofrotor rotation) that will displace the plunger 517 by an amountcorresponding to the desired dosage and then operate the motor 507 toachieve the desired displacement of the plunger 517. In this manner,delivery of the desired amount of fluid from the infusion device 502 tothe body 501 of the user is achieved.

Still referring to FIG. 8, while the foregoing discussion of the controlprocess 800 was described in the context of the sensing arrangement 504,600 detecting or otherwise identifying acceptable and/or unusablemeasurement samples and/or measurement sequences, modifying measurementsequences, and determining predicted measurement values, in alternativeembodiments, one or more of those aspects may be performed by theinfusion device 502 and/or the pump control system 520, 700. Forexample, in one alternative embodiment, the sensing arrangement 504, 600may merely obtain a new measurement value and transmit the newmeasurement value to the pump control system 520, 700, whereby the datamanagement application 710 on the pump control module 702 manages orotherwise maintains the sequence of recent measurement values anddetermines whether the new measurement value is acceptable. In suchembodiments, the pump control system 520, 700 may also account formeasurement values that may have been dropped or otherwise lost intransmission from the sensing arrangement 504, 600 that were notreceived by the communications interface 704. For example, if thesensing arrangement 504, 600 obtains and transmits a new measurementvalue every 5 minutes, the data management application 710 mayautomatically identify an absent measurement sample and update themeasurement sequence to reflect a new unusable measurement sample inresponse to a failure to receive a new measurement value 5 minutes (plusor minus a particular time window or margin for error) after the mostrecently obtained measurement sample. In a similar manner as describedabove, the data management application 710 on the pump control module702 may also detect or otherwise identify an unacceptable and/or invaliddata sequence and modify the measurement sequence using one or moreacceptable measurement values within the measurement sequence (e.g.,tasks 810, 812, 814, 816). Thereafter, the data prediction application712 on the pump control module 702 determines a predicted measurementvalue that is provided to the command generation application 714 forgenerating operating commands for the infusion device 502 (e.g., tasks818, 820), as described above.

In one or more embodiments, the sensing arrangement 504, 600 obtains newmeasurement values, updates the measurement sequences, and transmits themeasurement sequences with a corresponding indication of any unusablemeasurement values in a measurement sequence (e.g., tasks 802, 804, 806,808). In such embodiments, the data management application 710 on thepump control module 702 receives a measurement sequence from the sensingarrangement 504, 600 and determines whether the measurement sequenceneeds to be modified for subsequent usage (e.g., task 810). In thisregard, the data management application 710 may modify unusablemeasurement values indicated by the sensing arrangement 504, 600 whilealso accounting for any measurement samples that may have been droppedor otherwise lost in transmission from the sensing arrangement 504, 600.For example, the data management application 710 may also identifyabsent or missing measurement samples within a measurement sequencereceived from the sensing arrangement 504, 600 that were likely dropped,lost, or otherwise corrupted during transmission.

FIG. 9 is depicts a table 900 including exemplary measurement sequences,and FIG. 10 depicts a table 1000 corresponding to the measurementsequences in the table 900 of FIG. 9 after invalid and/or unacceptablemeasurement sequences have been modified and a corresponding predictedvalue based thereon has been calculated using a in conjunction with thecontrol process 800 described above. In FIG. 9, unusable measurementsamples are identified by setting the corresponding measurement value toa null value. As described above, the unusable measurement samples couldbe measurement samples that did not result in a valid measurement value(e.g., an original measurement value outside the range of valid valuesfor the sensing element 604), measurement samples having a lowsignal-to-noise ratio that are susceptible to being corrupted by noise,absent measurement samples that were lost or otherwise failed to bereceived by the infusion device 502, or the like. The first row of thetables 900, 1000 depicts a valid measurement sequence where all of theindividual measurement samples are originally valid and acceptable. Inthe illustrated embodiment, the predicted values depicted in the table1000 are calculated for the time 6 measurement samples into the future(e.g., h=6) with a tuning parameter of 0.3 (e.g., β=0.3).

The second row in the table 900 depicts a measurement sequence where adifference between two sequential usable measurement samples (e.g.,y_(t) and y_(t-4)) is equal to interpolatable number of measurementsamples (e.g., 3 measurement samples corresponding to an allowable gapof 20 minutes between y_(t) and y_(t-4)). The second row in table 1000depicts the modified measurement sequence obtained by performing linearinterpolation between the usable measurement values for y_(t) andy_(t-4) to replace the measurement samples between y_(t) and y_(t-4)with interpolated measurement values and the corresponding predictedmeasurement value calculated using those interpolated measurementvalues.

The third row in the table 900 depicts a measurement sequence where thedifference between usable measurement samples y_(t) and y_(t-6) and thedifference between usable measurement samples y_(t-4) and y_(t-1) areboth less than or equal to the interpolatable number of measurementsamples. The third row in table 1000 depicts the modified measurementsequence obtained by performing linear interpolation between the usablemeasurement values for y_(t-8) and y_(t-6) to obtain an interpolatedvalue for y_(t-7) and performing linear interpolation between the usablemeasurement values for y_(t-4) and y_(t-1) to obtain interpolated valuesfor y_(t-3) and y_(t-2).

The fourth row in the tables 900, 1000 depicts a modified measurementsequence where a usable measurement sample (e.g., y_(t-9)) from apreviously stored measurement sequence in memory 608, 706 is used tointerpolate and replace the oldest measurement sample(s) in a currentmeasurement sequence when the next preceding measurement value was anacceptable measurement value (e.g., y_(t-9)=1).

The fifth row in the table 900 depicts a measurement sequence where thedifference between two sequential usable measurement samples y_(t-1) andy_(t-6) is greater than the interpolatable number of measurementsamples. The fifth row in table 1000 depicts the modified measurementsequence obtained by backfilling or otherwise replacing measurementsamples older than y_(t-1) with the measurement value for y_(t-1). Inthis regard, originally acceptable measurement values for y_(t-6),y_(t-7), and y_(t-8) may be overwritten with the value of y_(t-1). Inthis manner, backfilling for y_(t-6), y_(t-7), and y_(t-8) eliminatesthe spike or jump that could otherwise occur when transitioning from theoriginal value of y_(t-6) (e.g., 2) to the backfilled value for y_(t-5)(e.g., 4.5) and effectively resets the prediction algorithm with thevalue of y_(t-1).

The sixth row in the tables 900, 1000 depicts a modified measurementsequence where the oldest measurement samples are unusable and replacedwith the value of the usable measurement sample that succeeds theunusable measurement samples in the sequence.

The seventh row in the table 900 depicts a measurement sequence wherethe oldest two measurement samples in the sequence are unusable andcannot be interpolated because the preceding measurement sample (e.g.,y_(t-9)) is unavailable or unusable. At the same time, the differencebetween usable samples y_(t-3) and y_(t-6) is less than theinterpolatable number of measurement samples. In this regard, theseventh row in table 1000 depicts the modified measurement sequenceobtained by backfilling or otherwise replacing measurement samplesy_(t-7) and y_(t-8) with the usable measurement value for y_(t-6), whilealso performing linear interpolation between the usable measurementvalues for y_(t-3) and y_(t-6) to obtain interpolated values for y_(t-4)and y_(t-5).

As described above, by virtue of calculating the predicted measurementvalue in a deterministic manner rather than a recursive manner, anymeasurement values that are invalid, unacceptable, or otherwise missingfrom a measurement sequence may be interpolated or replaced usingacceptable measurement value(s) to obtain a modified measurementsequence, which may then be utilized to calculate a predictedmeasurement value without compromising the accuracy and/or reliabilityof the prediction. In this regard, a predicted measurement value remainsavailable to the pump control system 520, 700 for influencing operationof the infusion device 502, rather than having to disable the predictivecontrol and wait until a complete and valid measurement sequence isavailable before resuming the predictive control.

Referring now to FIG. 11, in one or more exemplary embodiments, a pumpcontrol system 1100 suitable for use as the pump control system 520 inFIG. 5 includes or otherwise implements a patient monitoring application1116 configured automatically adjust the infusion device operating modeimplemented by the command generation application 1114 and/or the pumpcontrol system 1100. It should be appreciated that the various elementsof the pump control system 1100 are similar to counterpart elementsdescribed above in the context of the pump control system 700 of FIG. 7,and accordingly, such common features and/or functionality may not beredundantly described here in the context of FIG. 11. In this regard,the control module 1102 reads and executes the computer-executableprogramming instructions stored on the data storage element 1106 (ormemory) to implement or otherwise generate the monitoring application1116 in conjunction with the applications 710, 712, 1114 and perform thetasks, operations, functions, and processes described in greater detailbelow.

In the illustrated embodiment, the pump control module 1102 is coupledto one or more user interface elements 1120 to receive or otherwiseobtain one or more user-configurable threshold values used by themonitoring application 1116 to automatically control the operating modeimplemented by the command generation application 1114, such as, forexample, a suspend protection threshold (SPT) value, a resume deliveryprotection threshold value, a minimum IOB threshold value, or the like.Thus, the one or more user interface element(s) 1120 include at leastone input user interface element, such as, for example, a button, akeypad, a keyboard, a knob, a joystick, a mouse, a touch panel, atouchscreen, a microphone or another audio input device, and/or thelike. The user input values obtained via a user interface element 1120may be stored or otherwise maintained in the memory 1106 for futurereference by the monitoring application 1116 during operation of thepump control system 1100. For example, the memory 1106 may include adedicated register associated with the suspend delivery protection valuethat stores the SPT value received from a user via an input userinterface element 1120.

Additionally, the pump control module 1110 may receive or otherwiseobtain alert configuration information for the user associated with theinfusion device 502 and generate or otherwise provide notifications tothe user in accordance with that user's alert configuration whileoperating the infusion device 502. Accordingly, to generate usernotifications according to the user's alert configuration information,the one or more user interface element(s) 1120 include at least oneoutput user interface element, such as, for example, a display element(e.g., a light-emitting diode or the like), a display device (e.g., aliquid crystal display or the like), a speaker or another audio outputdevice, a haptic feedback device, or the like. In a similar manner asdescribed above, the user's alert configuration information obtained viaa user interface element 1120 may be stored or otherwise maintained inthe memory 1106 for future reference during operation of the pumpcontrol system 1100. In practice, one or more of the user interfaceelement(s) 1120 may be integrated with the infusion device 502, oralternatively, be integrated in another component of an infusion system(e.g., the CCD 106, the computer 108, or the like) that iscommunicatively coupled to the infusion device 502 and/or the pumpcontrol system 520, 1100 as described above in the context of FIG. 1(e.g., to support text messages, e-mails, or other remote usernotifications).

In one or more exemplary embodiments, the monitoring application 1116calculates or otherwise determines one or more thresholds used tocontrol operation of the infusion device 502 based on the SPT valueinput by the user. The monitoring application 1116 may calculate orotherwise determine a predictive suspend threshold value by adding anoffset value to the SPT value. In one embodiment, the offset value isfixed at an empirically determined value that achieves the desiredtradeoff between the rate or frequency at which delivery is likely to besuspended and the rate or frequency at which the SPT value is likely tobe violated. In this regard, increasing the offset value is likely toincrease the suspend frequency and reduce the likelihood of the SPTvalue being violated, while decreasing the offset value is likely todecrease the suspend frequency and increase the likelihood of the SPTvalue being violated. For example, in one embodiment, the monitoringapplication 1116 adds an offset of 20 mg/dL to the SPT value to obtainthe predictive suspend threshold value. In alternative embodiments, thepredictive suspend threshold value may be calculated by multiplying theSPT value by a conversion factor. In exemplary embodiments, thepredictive suspend threshold value is greater than or equal to the SPTvalue.

In a similar manner, the monitoring application 1116 calculates orotherwise determines a suspend enable threshold (SET) value having avalue that is greater than the predictive suspend threshold value basedon the SPT value and/or the predictive suspend threshold value. In oneembodiment, the monitoring application 1116 adds an additional offset of50 mg/dL to the SPT value in addition to the 20 mg/dL offset to obtainthe SET value. In this regard, the additional offset is chosen toprevent delivery from being suspended prematurely while the user'scurrent glucose is relatively high. Alternatively, the SET value may becalculated by multiplying the SPT value by another conversion factor. Insome embodiments, the predictive suspend threshold value and the SETvalue calculated by the monitoring application 1116 may also be storedin the memory 1106 (e.g., in dedicated registers). Thus, it will beappreciated that in some alternative embodiments, the predictive suspendthreshold value and the SET value may be user-configurable, in a similarmanner as described above in the context of the SPT value. Inalternative embodiments, the offset values or conversion factors used tocalculate the predictive suspend threshold value and the SET value arestored in the memory 1106 and used to calculate the predictive suspendthreshold value and the SET value at run time. In such embodiments, theoffset values or conversion factors may be user-configurable.

As described in greater detail below in the context of FIG. 12, thecurrent glucose measurement value is below the SET value before thesuspend delivery mode is entered. When the current glucose measurementvalue is less than the SET value, the predicted blood glucose value isless than the predictive suspend threshold value, and predictivedelivery suspension is enabled by the user, the monitoring application1116 automatically signals, commands, or otherwise instructs the commandgeneration application 1114 to enter or otherwise implement a suspenddelivery mode during which insulin delivery is disabled. Alternatively,when the current glucose measurement value is less than both the SETvalue and the SPT value, the monitoring application 1116 automaticallysignals, commands, or otherwise instructs the command generationapplication 1114 to enter or otherwise implement the suspend deliverymode as long as automatic delivery suspension is enabled, regardless ofwhether predictive delivery suspension is enabled.

Still referring to FIG. 11, the monitoring application 1116 alsocalculates or otherwise determines one or more thresholds used to resumedelivery of infusion based on the SPT value. The monitoring application1116 may calculate or otherwise determine a resume enable threshold(RET) value by adding an offset value to the SPT value. In one exemplaryembodiment, the offset value for determining the RET value is fixed andequal to the same offset value (e.g., 20 mg/dL) that is added to the SPTvalue to obtain the predictive suspend threshold value; however, inother embodiments, the offset value for determining the RET value may begreater than or less than the offset value that is added to the SPTvalue to obtain the predictive suspend threshold value. In this regard,the RET value is greater than the SPT value by at least an amount thatmakes it unlikely that the current glucose measurement value will reachthe SPT value after delivery is re-enabled but before delivery can bere-suspended. Additionally, the monitoring application 1116 calculatesor otherwise determines a predictive resume threshold value based on theSPT value and/or the RET value. In this regard, the predictive resumethreshold value is greater than the RET value to ensure that thepredicted blood glucose value is sufficiently above the SPT value andthe RET value (e.g., on an upward trend) so that there is unlikely to bea need for the infusion device 502 to revert to the suspend deliverymode until at least a refractory period has elapsed after resumingdelivery. For example, the monitoring application 1116 may add anadditional offset of 20 mg/dL to the RET value (or alternatively, add 40mg/dL to the SPT value). In a similar manner as described above, the RETvalue and the predictive resume threshold value calculated by themonitoring application 1116 may be stored in the memory 1106, oralternatively, the offset values or conversion factors used to calculatethe RET value and the predictive resume threshold value may be stored inmemory 1106 for calculation at run time. Likewise, in some embodiments,the RET value and the predictive resume threshold value (oralternatively, the offset values or conversion factors used to calculatethem) may be user-configurable.

As described in greater detail below in the context of FIG. 13, in oneor more embodiments, the suspend delivery mode is exited when thecurrent glucose measurement value is greater than the RET value and thepredicted glucose value is greater than the predictive resume thresholdvalue. When the current glucose measurement value and the predictedblood glucose value are greater than the RET value and the predictiveresume threshold value, respectively, the monitoring application 1116automatically signals, commands, or otherwise instructs the commandgeneration application 1114 to exit the suspend delivery mode and enteror otherwise implement another operating mode during which insulindelivery is enabled. For example, the command generation application1114 may resume generating delivery (or dosage) commands to provide abasal infusion rate in an open-loop delivery control mode, oralternatively, by implementing a closed-loop control scheme configuredto regulate the user's current glucose measurement value to a particulartarget blood glucose value by minimizing the difference between thecurrent glucose measurement value and the target blood glucose value, asdescribed in greater detail below in the context of FIG. 22.

Still referring to FIG. 11, in exemplary embodiments, the monitoringapplication 1116 is configured to implement one or more timers to ensurethat the infusion device does not toggle between operating modes. In oneembodiment, a minimum suspension time period is imposed, such that themonitoring application 1116 does not signal the command generationapplication 1114 to transition from the suspend delivery mode to anotherdelivery mode until implementing the suspend delivery mode for at leastthe minimum suspension time period. In this regard, the suspend deliverymode may be maintained if the minimum suspension time period has notelapsed even if the current glucose measurement value is greater thanthe RET value and the predicted blood glucose value is greater than thepredictive resume threshold value. In exemplary embodiments, the minimumsuspension time period is fixed at thirty minutes, however, inalternative embodiments, the minimum suspension time period may beuser-configurable. Additionally, a maximum suspension time period may beimposed, such that suspend delivery mode is not implementedindefinitely. In this regard, the infusion device may be transitioned toa normal delivery mode if the maximum suspension time period has elapsedeven if the current glucose measurement value is less than the RET valueand the predicted blood glucose value is less than the predictive resumethreshold value. In exemplary embodiments, the maximum suspension timeperiod is fixed at two hours, however, in alternative embodiments, themaximum suspension time period may be user-configurable.

In exemplary embodiments, a minimum delivery time period is also imposedto provide a minimum refractory period before the infusion device 502can revert back to the suspend delivery mode. In this regard, the normaldelivery mode may be maintained if the minimum delivery time period hasnot elapsed even if the current glucose measurement value is less thanthe SET value and the predicted blood glucose value is less than thepredictive suspend threshold value. In exemplary embodiments, theminimum delivery time period is also fixed at thirty minutes, however,in alternative embodiments, the minimum delivery time period may beuser-configurable. As described in greater detail below in the contextof FIGS. 12-13, in exemplary embodiments, the refractory periodimplemented by the monitoring application 1116 is dynamically determinedbased on the responsiveness of the user. In this regard, aftertransitioning from the suspend delivery mode after the maximumsuspension time period has elapsed, the monitoring application 1116 maygenerate or otherwise provide a notification to the user via a userinterface element 1120 that identifies or otherwise indicates that thedelivery was suspended for the maximum suspension time period. If theuser is not responsive to the notification and an acknowledgment inputhas not been received via the user interface element(s) 1120, a maximumrefractory time period may be imposed before the infusion device 502 isallowed to revert back to the suspend delivery mode. Conversely, if auser acknowledgment response is received via a user interface element1120, the refractory time period is set to be equal to the minimumdelivery time period.

FIG. 12 depicts an exemplary delivery suspension process 1200 suitablefor implementation by a control system associated with a fluid infusiondevice, such as the pump control system 520, 1100 in the infusion device502, to automatically suspend fluid delivery based on current andpredicted values for a physiological condition of a user (or patient).The various tasks performed in connection with the delivery suspensionprocess 1200 may be performed by hardware, firmware, software executedby processing circuitry, or any combination thereof. For illustrativepurposes, the following description may refer to elements mentionedabove in connection with FIGS. 1-7 and 11. In practice, portions of thedelivery suspension process 1200 may be performed by different elementsof the control system 500, such as, for example, the infusion device502, the sensing arrangement 504, the pump control system 520, 1100, thepump control module 1102, the motor control module 512, and/or the motor507. It should be appreciated that the delivery suspension process 1200may include any number of additional or alternative tasks, the tasksneed not be performed in the illustrated order and/or the tasks may beperformed concurrently, and/or the delivery suspension process 1200 maybe incorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Moreover, oneor more of the tasks shown and described in the context of FIG. 12 couldbe omitted from a practical embodiment of the delivery suspensionprocess 1200 as long as the intended overall functionality remainsintact.

In exemplary embodiments, the delivery suspension process 1200 isperformed when automatic delivery suspension is enabled (e.g., after theuser has manipulated the user interface 1120 to enable automaticdelivery suspension) and the infusion device is not currently beingoperated in a mode where delivery is suspended. As illustrated in FIG.12, the delivery suspension process 1200 may repeat indefinitely whileautomatic delivery suspension is enabled until identifying or otherwisedetermining that operation of the infusion device should be suspended.

In the illustrated embodiment, the delivery suspension process 1200begins by receiving or otherwise obtaining current and predicted valuesfor the physiological condition of the user being monitored andidentifying or otherwise determining whether those values are valid(tasks 1202, 1204). In this regard, the monitoring application 1116receives or otherwise obtains the current glucose measurement for theuser obtained by the sensing arrangement 504, 600 and/or sensing element604 along with a predicted blood glucose value for the user at somepoint in the future from the data prediction application 612 and/orprediction application 712. The monitoring application 1116 verifies orotherwise confirms that neither the current glucose measurement valuenor the predicted blood glucose value are flagged or otherwise marked asbeing invalid or unusable.

In response to identifying that the current glucose measurement valueand/or the predicted blood glucose value are invalid or unusable, thedelivery suspension process 1200 continues by maintaining operation ofthe infusion device in the current delivery mode (task 1218). If thecurrent delivery mode is an open-loop basal delivery mode, the commandgeneration application 1114 continues generating delivery (or dosage)commands configured to maintain a particular basal infusion rate for theuser. In other embodiments, if the current delivery mode is a PIDclosed-loop delivery mode, the command generation application 1114continues generating delivery commands using the current glucosemeasurement value and/or the predicted blood glucose value. For example,if the current glucose measurement value is valid and usable, thecommand generation application 1114 may calculate or otherwise determinea difference between the current glucose measurement value and a targetblood glucose reference value (or glucose setpoint) and applyproportional-integral-derivative (PID) control parameters to thedifference to arrive at a delivery command configured to regulate thecurrent glucose measurement value to the target blood glucose referencevalue, as described in greater detail below in the context of FIG. 22.Conversely, if the current glucose measurement value is invalid orunusable, the command generation application 1114 may determine adelivery command based on the user's current insulin on board withoutrelying on the current glucose measurement from the sensing arrangement504, as described in greater detail below in the context of FIG. 21.Alternatively, if the current glucose measurement value is invalid orunusable, the command generation application 1114 may identify a defaultdelivery command configured to maintain a particular infusion rate untila subsequently received current glucose measurement value is valid andusable. As described above, the delivery command generated by thecommand generation application 1114 is provided to the motor controlmodule 512, which, in turn, operates the motor 507 to displace theplunger 517 and infuse or otherwise deliver insulin to the body 501 ofthe user.

When the current glucose measurement value and the predicted bloodglucose value are both valid and usable, the delivery suspension process1200 continues by identifying or otherwise determining whether theduration for which the infusion device has been operated in the deliverymode is greater than a refractory time period (task 1206). When theinfusion device has been operated in the current delivery mode for lessthan the refractory time period, the delivery suspension process 1200continues by maintaining operation of the infusion device in the currentdelivery mode (task 1218). As described above, the monitoringapplication 1116 implements or otherwise provides a timer that tracks orotherwise monitors the duration of time for which the command generationapplication 1114 implements a delivery mode to impose a refractory timeperiod before the command generation application 1114 can revert back toimplementing a suspend delivery mode, thereby providing a recoveryperiod after transitioning from the suspend delivery mode to a deliverymode. In exemplary embodiments, the refractory period imposed by themonitoring application 1116 is dynamically determined based on theresponsiveness of the user. In this regard, if the user has beenclassified as responsive, the monitoring application 1116 verifies,confirms, or otherwise ensures that the command generation application1114 has implemented the delivery mode continuously for at least theminimum delivery time period (e.g., thirty minutes) before proceeding.Alternatively, when the user is nonresponsive, the monitoringapplication 1116 confirms that the command generation application 1114has implemented the delivery mode continuously for at least the maximumrefractory time period (e.g., four hours) before proceeding. It shouldbe noted that in some embodiments, in response to the automatic deliverysuspension being enabled, the refractory time period may be initializedat zero because delivery has not yet been suspended.

If the refractory period currently being imposed has elapsed, thedelivery suspension process 1200 continues by identifying or otherwisedetermining whether predictive automatic delivery suspension has beenenabled by the user (task 1208). When predictive automatic deliverysuspension is enabled, the delivery suspension process 1200 continues byidentifying or otherwise determining whether the predicted value is lessthan the predictive suspend threshold value (task 1210). If thepredicted value is less than the predictive suspend threshold value, thedelivery suspension process 1200 continues by identifying or otherwisedetermining whether the current measurement value is less than thesuspend enable threshold value and suspending delivery when the currentmeasurement value is less than the suspend enable threshold value (tasks1212, 1214). Otherwise, if the predicted value is greater than thepredictive suspend threshold value or the current measurement value isgreater than the suspend enable threshold value, the delivery suspensionprocess 1200 maintains delivery in a similar manner as described above(task 1218).

When predictive automatic delivery suspension is enabled, the monitoringapplication 1116 determines whether the user's predicted blood glucosevalue is less than the predictive suspend threshold value determinedbased on the SPT value set by the user. When the user's predicted bloodglucose value is less than the predictive suspend threshold value, themonitoring application 1116 confirms that the current blood glucosemeasurement for the user is also less than the SET value. When theuser's predicted blood glucose value is less than the predictive suspendthreshold value and the current blood glucose measurement is also lessthan the SET value, the monitoring application 1116 automaticallysignals, commands, or otherwise instructs the command generationapplication 1114 to implement a suspend delivery mode where any nonzerodelivery commands are disabled, deactivated, or otherwise prevented frombeing implemented by the motor control module 512. For example, themonitoring application 1116 may signal the command generationapplication 1114 to disable a delivery command generated using the PIDcontrol parameters and provide a delivery command of zero to the motorcontrol module 512, thereby preventing further displacement of theplunger 517 and suspending delivery of insulin to the body 501 of theuser. In other embodiments, the monitoring application 1116 may causethe pump control module 1102 to output a flag signal that indicates, tothe motor control module 512, that any delivery commands output by thecommand generation application 1114 should be ignored or otherwisedisregarded. Additionally, depending on the embodiment, the monitoringapplication 1116 may interact with an output user interface 1120 togenerate or otherwise provide an auditory and/or visual notificationthat indicates, to the user, that insulin delivery is being suspended.The user notifications may be generated in accordance with user-specificand/or user-configurable alert configuration information, in a similarmanner as described in U.S. patent application Ser. No. 14/174,487,which is incorporated by reference herein. In other embodiments, theconfiguration settings for user notifications when automatic deliverysuspension is enabled may be fixed and maintained in memory 1106 in amanner that does not allow the user to modify the notification settings.

In alternative embodiments, if predictive automatic delivery suspensionis disabled by the user but automatic suspension based on the suspendprotection threshold is enabled, the delivery suspension process 1200continues by identifying or otherwise determining whether the currentmeasurement value is less than the suspend protection threshold valueand suspending delivery when the current measurement value is less thanthe protection threshold value (tasks 1214, 1216). In this regard, themonitoring application 1116 determines whether the current glucosemeasurement value is less than the SPT value set by the user. When theuser's current glucose measurement value is less than the SPT, themonitoring application 1116 automatically signals, commands, orotherwise instructs the command generation application 1114 and/or themotor control module 512 to implement a suspend delivery mode in asimilar manner as described above, thereby preventing furtherdisplacement of the plunger 517 and suspending infusion of insulin tothe body 501 of the user.

FIG. 13 depicts an exemplary delivery resumption process 1300 suitablefor implementation by a control system associated with a fluid infusiondevice, such as the pump control system 520, 1100 in the infusion device502, in conjunction with the delivery suspension process 1200 of FIG. 12to automatically resume fluid delivery based on current and predictedvalues for the physiological condition of the user (or patient). Thevarious tasks performed in connection with the delivery resumptionprocess 1300 may be performed by hardware, firmware, software executedby processing circuitry, or any combination thereof. For illustrativepurposes, the following description may refer to elements mentionedabove in connection with FIGS. 1-7 and 11. In practice, portions of thedelivery resumption process 1300 may be performed by different elementsof the control system 500, such as, for example, the infusion device502, the sensing arrangement 504, the pump control system 520, 1100, thepump control module 1102, the motor control module 512, and/or the motor507. It should be appreciated that the delivery resumption process 1300may include any number of additional or alternative tasks, the tasksneed not be performed in the illustrated order and/or the tasks may beperformed concurrently, and/or the delivery resumption process 1300 maybe incorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Moreover, oneor more of the tasks shown and described in the context of FIG. 13 couldbe omitted from a practical embodiment of the delivery resumptionprocess 1300 as long as the intended overall functionality remainsintact.

In exemplary embodiments, the delivery resumption process 1300 isperformed after the infusion device has automatically entered anoperating mode where delivery is suspended or otherwise disabled (e.g.,suspend delivery mode at task 1214) as a result of the deliverysuspension process 1200 to prevent fluid infusion to a user. Asillustrated in FIG. 13, the delivery resumption process 1300 may repeatindefinitely while delivery is suspended until identifying or otherwisedetermining that operation of the infusion device to deliver fluidshould be resumed.

In the illustrated embodiment, the delivery resumption process 1300begins by receiving or otherwise obtaining current and predicted valuesfor the physiological condition of the user being monitored, identifyingor otherwise determining whether the duration for which the infusiondevice has been operated in the suspend delivery mode is greater than amaximum suspension time period, and automatically resuming delivery offluid using the current value for the physiological condition of theuser when the current suspend duration is greater than the maximumsuspension time period (tasks 1302, 1304, 1318). In this regard, afterdetermining to suspend delivery, the monitoring application 1116initializes a timer to monitor the duration of time for which thesuspended delivery mode is implemented. When the current suspendduration is greater than the maximum suspension time period (e.g., twohours), the monitoring application 1116 automatically transitions theinfusion device from the suspend delivery mode to another delivery mode.For example, the monitoring application 1116 may automatically signal,command, or otherwise instruct the command generation application 1114to resume generating delivery commands and providing the deliverycommands to the motor control module 512. Alternatively, the monitoringapplication 1116 may cause the pump control module 1102 to de-assert orotherwise remove a suspend delivery flag signal to indicate, to themotor control module 512, that delivery commands output by the commandgeneration application 1114 should now be implemented or otherwiseutilized to operate the motor 507. Additionally, depending on theembodiment, the monitoring application 1116 may interact with an outputuser interface 1120 to generate or otherwise provide an auditory and/orvisual notification that indicates, to the user, that the maximumsuspension time period has been met or exceeded and the suspend deliverymode has been automatically terminated.

When the maximum suspension time period has not elapsed since enteringthe suspend delivery mode, the delivery resumption process 1300continues by identifying or otherwise determining whether the automaticdelivery suspension has been disabled by the user and resuming deliveryof fluid using the current value for the physiological condition of theuser in response to detecting that automatic delivery suspension isdisabled (tasks 1306, 1318). In this regard, if the user manipulates theuser interface element 1120 to disable the automatic delivery suspension(e.g., delivery suspension process 1200), the monitoring application1116 automatically signals, commands, or otherwise instructs the commandgeneration application 1114 and/or the motor control module 512 toterminate the suspend delivery mode and begin implementing anotheroperating mode where delivery is enabled.

When automatic delivery suspension remains enabled, the deliveryresumption process 1300 continues by identifying or otherwisedetermining whether the current and predicted values for thephysiological condition of the user are valid before identifying orotherwise determining whether the current value for the physiologicalcondition is greater than a resume enable threshold (tasks 1308, 1310).When the current value for the physiological condition is greater thanthe resume enable threshold, the delivery resumption process 1300continues by identifying or otherwise determining whether the predictedvalue for the physiological condition is greater than a predictiveresume threshold (task 1312). When the predicted value is also greaterthan its corresponding resume threshold, the delivery resumption process1300 verifies or otherwise confirms that the duration for which theinfusion device has been operated in the suspend delivery mode isgreater than a minimum suspension time period before resuming delivery(tasks 1314, 1318).

After the monitoring application 1116 verifies or otherwise confirmsthat neither the current glucose measurement value nor the predictedblood glucose value are flagged or otherwise marked as being invalid orunusable, the monitoring application 1116 compares the current glucosemeasurement value to the RET value. After the monitoring application1116 determines the current glucose measurement value is greater thanthe RET value, the monitoring application 1116 determines whether thepredicted blood glucose value is greater than the predictive resumethreshold value. After identifying that both current glucose measurementvalue is greater than the RET value and the predicted blood glucosevalue is greater than the predictive resume threshold value, themonitoring application 1116 confirms that the current suspend durationis greater than the minimum suspension time period (e.g., thirtyminutes). When the minimum suspension time period has elapsed, themonitoring application 1116 automatically transitions the infusiondevice from the suspend delivery mode to another delivery mode, such asa closed-loop delivery mode, for example, by signaling the commandgeneration application 1114 and/or the motor control module 512 toresume implementing the normal closed-loop delivery mode.

In exemplary embodiments, when the delivery resumption process 1300determines delivery should be resumed, the delivery resumption process1300 also identifies or otherwise determines a suspension refractorytime period for which the infusion device should be maintained in adelivery mode before the delivery suspension process 1200 canautomatically transition the infusion device back to a suspendeddelivery mode (task 1320). In one or more embodiments, the monitoringapplication 1116 determines the refractory time period is equal to amaximum refractory time period (e.g., four hours) after determining thatthe current suspend duration is greater than or equal to the maximumsuspend duration and the monitoring application 1116 has not identified,received, or otherwise detected user input via the user interfaceelement(s) 1120. In this regard, absent the user manipulating an inputuser interface element 1120 to respond to a user notification generatedby the monitoring application 1116 that indicates the maximum suspensiontime period has been met or exceeded, the monitoring application 1116classifies the user as nonresponsive and imposes the maximum refractorytime period until a user response is detected. Otherwise, when the useris responsive (e.g., by manually resuming delivery, disabling theautomatic delivery suspension, responding to user notifications, or thelike) or the monitoring application 1116 determines delivery should beresumed based on the user's glucose values (e.g., at tasks 1310, 1312and 1314), the monitoring application 1116 sets the refractory timeperiod to be equal to a minimum delivery time period (e.g., thirtyminutes). Thereafter, the delivery suspension process 1200 imposes therefractory period determined by the delivery resumption process 1300(e.g., at task 1206) before transitioning the infusion device back to asuspend delivery mode.

Still referring to FIG. 13, in exemplary embodiments, the deliveryresumption process 1300 maintains the infusion device in the suspenddelivery mode (task 1324) when one of the values for the physiologicalcondition of the user is invalid, the current value for thephysiological condition is less than the resume enable threshold, thepredicted value for the physiological condition is less than thepredictive resume threshold, and/or the duration of suspend deliverymode is less than the minimum suspension time period. In the illustratedembodiment, however, the delivery resumption process 1300 verifies orotherwise confirms the amount of infused fluid that is currently activein the body of the user is greater than a minimum threshold amount ofactive fluid in the user's body prior to maintaining suspended delivery(task 1322). In this regard, as described in greater detail below in thecontext of FIGS. 20-21, the delivery resumption process 1300 may beintegrated with or otherwise implemented in conjunction with an IOBmonitoring process 2000, whereby the delivery resumption process 1300also confirms or otherwise verifies that the current IOB in the body ofthe user is greater than a minimum IOB for the user before maintainingthe infusion device in the suspend delivery mode. In response todetermining the current IOB for the user is less than the minimum JOB,the delivery resumption process 1300 determines to resume delivery andautomatically transitions the infusion device from the suspendeddelivery mode to a delivery mode that is augmented or otherwise adjustedto regulate the user's IOB (task 1318). In such embodiments, rather thanregulating the physiological condition of the user influenced by theinfused fluid (e.g., the user's blood glucose level), the infusiondevice is operated to regulate the active amount of infused fluid in theuser's body. For example, in response to determining to resume deliverybased on the current IOB for the user being less than the minimum JOB,the monitoring application 1116 may signal, command, or otherwiseinstruct the command generation application 1114 to implement orotherwise support the IOB control process 2100 of FIG. 21, as describedin greater detail below. In such embodiments, the delivery suspensionprocess 1200 may impose a refractory period determined by the deliveryresumption process 1300 (e.g., at task 1206) before transitioning theinfusion device from the IOB delivery control mode back to a suspenddelivery mode. In one embodiment, the maximum refractory time period(e.g., four hours) is imposed before transitioning the infusion devicefrom the IOB delivery control mode back to a suspend delivery mode.

FIGS. 14-19 are graphs depicting the relationship between the currentglucose measurement values for the user with respect to time for variousembodiments of the delivery suspension process 1200 of FIG. 12 inconjunction with the delivery resumption process 1300 of FIG. 13 whenautomatic delivery suspension is enabled using a SPT value of 70 mg/dL.In some embodiments, the graphs may be presented on a display associatedwith any device of an infusion system, such as, for example, on adisplay element 226, 1120 of an infusion device 102, 200, 502 or adisplay associated with another device 106, 108 in the infusion system100. It should be appreciated that FIGS. 14-19 are provided primarily toaid in understanding of the subject matter described herein and are notintended to be limiting. In this regard, numerous different combinationsand/or scenarios of glucose values, user notifications, and userresponses are likely to occur in practical embodiments of the subjectmatter described herein.

Turning to the graph 1400 in FIG. 14, at a first time t₁, the monitoringapplication 1116 automatically signals, commands, or otherwise instructsthe command generation application 1114 and/or the motor control module512 to operate in a suspend delivery mode when the user's predictedblood glucose value is less than the predictive suspend threshold value(e.g., 20 mg/dL plus the SPT value) and the current glucose measurementvalue 1402 is less than the SET value of 140 mg/dL (e.g., a 50 mg/dLoffset added to the predictive suspend threshold value). Additionally,the monitoring application 1116 may interact with the user interfaceelement(s) 1120 to generate or otherwise provide a notification to theuser that the infusion device 502 has automatically entered the suspenddelivery mode at time t₁.

At time t₂, the monitoring application 1116 automatically operates theuser interface element(s) 1120 to generate or otherwise provide one ormore low glucose notifications when current glucose measurement value1402 is less than or equal to the SPT value of 70 mg/dL. In this regard,if the user does not acknowledge or otherwise respond to the low glucosenotifications, the monitoring application 1116 may progressivelyescalate the low glucose notifications (e.g., by progressivelyincreasing the volume, frequency, vibration magnitude, brightness,visibility, or the like) until receiving a response from the user and/oruntil the current glucose measurement value 1402 rises above the SPTvalue.

In the illustrated embodiment, at time t₃, the monitoring application1116 automatically signals, commands, or otherwise instructs the commandgeneration application 1114 and/or the motor control module 512 toresume operating in a delivery mode when the user's predicted bloodglucose value is greater than the predictive resume threshold value of110 mg/dL (e.g., an offset of 20 mg/dL added to the RET value and/or anoffset of 40 mg/dL added to the SPT value) and the current glucosemeasurement value 1402 is greater than the RET value of 90 mg/dL (e.g.,an offset of 20 mg/dL added to the SPT value). In one or moreembodiments, because the determination to resume delivery is based on anincrease in the user's current and/or predicted glucose values, themonitoring application 1116 automatically sets the refractory period tothe minimum delivery time period of thirty minutes. Additionally, themonitoring application 1116 may interact with the user interfaceelement(s) 1120 to generate or otherwise provide a notification to theuser that the infusion device 502 has automatically resumed operating ina delivery mode at time t₃.

Turning now to the graph 1500 of FIG. 15, in a similar manner asdescribed above in the context of FIG. 14, at a first time t₁, themonitoring application 1116 automatically signals, commands, orotherwise instructs the command generation application 1114 and/or themotor control module 512 to operate in a suspend delivery mode when boththe user's predicted glucose value is less than the predictive suspendthreshold value and the user's current glucose measurement value 1502 isless than the SET value. At time t₂, the monitoring application 1116identifies or otherwise determines that both the user's predicted bloodglucose value is greater than the predictive resume threshold value andthe current glucose measurement value 1502 is greater than the RET valueof 90 mg/dL, however, the monitoring application 1116 maintainsoperation of the infusion device 502 in the suspend delivery modebecause the minimum suspension time period has not elapsed since timet₁. At time t₃, after a minimum suspension time period of thirty minuteshas elapsed since time t₁, the monitoring application 1116 automaticallysignals, commands, or otherwise instructs the command generationapplication 1114 and/or the motor control module 512 to resume operatingin a delivery mode and sets the refractory period to the minimumdelivery time period when both the user's predicted glucose value isgreater than the predictive resume threshold value and the currentglucose measurement value 1502 is greater than the RET value.

In the graph 1600 of FIG. 16, in a similar manner as described above inthe context of FIG. 14, the monitoring application 1116 automaticallysignals, commands, or otherwise instructs the command generationapplication 1114 and/or the motor control module 512 to operate in asuspend delivery mode when both the user's predicted blood glucose valueis less than the predictive suspend threshold value and the user'scurrent glucose measurement value 1602 is less than the SET value attime t₁, and the monitoring application 1116 automatically operates theoutput user interface element(s) 1120 to generate or otherwise provideone or more low glucose notifications when the current glucosemeasurement value 1602 is less than or equal to the SPT value at timet₂.

At time t₃, the monitoring application 1116 identifies or otherwisedetermines that the current suspend duration is greater than or equal tothe maximum suspend time period of two hours, and in response, themonitoring application 1116 automatically signals, commands, orotherwise instructs the command generation application 1114 and/or themotor control module 512 to resume operating in a delivery mode eventhough the user's predicted blood glucose value may be less than thepredictive resume threshold value and/or the current glucose measurementvalue 1602 is less than the RET value. It should be noted, however, thateven though the command generation application 1114 and/or the motorcontrol module 512 may be operating in a mode where delivery is enabled,actual fluid delivery to the body of the user does not necessarily occurat all times for some delivery modes. For example, a closed-loopdelivery mode may not deliver any insulin during periods when the user'scurrent glucose measurement value being less than the target glucosevalue resulting in delivery commands equal to zero (e.g., becausenegative infusion is not possible).

In exemplary embodiments, the monitoring application 1116 interacts withthe user interface element(s) 1120 to generate or otherwise provide anotification to the user that indicates the infusion device 502 hasautomatically resumed operating in a delivery mode at time t₃ based onthe maximum suspend duration being met rather than an increase in theuser's current and/or predicted blood glucose. In particular for theembodiment of FIG. 16 where the current glucose measurement value 1602is below the SPT value after the maximum suspend duration has elapsed,the monitoring application 1116 may generate or otherwise provide one ormore urgent notifications to increase the likelihood of the userconsuming carbohydrates, recalibrating and/or replacing the sensingarrangement 504, or otherwise engaging in activities likely to remedyany potential hypoglycemic event. In one or more embodiments, theconfiguration settings for these urgent resume notifications are fixedand not user-configurable to ensure users are always alerted when thesuspend delivery mode is automatically terminated while the user'scurrent glucose measurement value 1602 is below the SPT value.

As described above in the context of FIGS. 12-13, in embodiments wherethe suspend delivery mode is terminated based on the maximum suspendtime period elapsing and the monitoring application 1116 fails toreceive an acknowledgment or response to the user notification, themonitoring application 1116 automatically sets the refractory period tothe maximum refractory time period of four hours. Thereafter, asdescribed in greater detail below in the context of FIGS. 18-19, themonitoring application 1116 may dynamically reduce the refractory timeperiod (e.g., from four hours to the minimum delivery time of thirtyminutes) upon receiving an acknowledgment or response to the usernotification prior to four hours elapsing since time t₃.

The graph 1700 of FIG. 17 is similar to the graph 1600 of FIG. 16 butdepicts an embodiment where the user's current glucose measurement value1702 is greater than the SPT value at time t₃. In this regard, theautomatically signals, commands, or otherwise instructs the commandgeneration application 1114 and/or the motor control module 512 toresume operating in a delivery mode based on the difference between timet₃ and time t₁ being greater than or equal to the maximum suspensiontime period, as described above. In the embodiment of FIG. 17, themonitoring application 1116 operates the output user interfaceelement(s) 1120 to generate or otherwise provide a notification to theuser that the infusion device 502 has automatically resumed operating ina delivery mode based on the maximum suspend duration being met.However, these user notifications may have reduced urgency associatedtherewith (e.g., fewer notifications, lower intensity and/or frequencyof notifications, or the like) relative to the urgent resumenotifications generated when the current glucose measurement value 1602is less than the SPT value because the user's current glucosemeasurement value 1702 is greater than the SPT value.

Turning now to the graph 1800 of FIG. 18, at time t₁, the monitoringapplication 1116 automatically signals the command generationapplication 1114 and/or the motor control module 512 to operate in asuspend delivery mode when the user's predicted glucose value is lessthan the predictive suspend threshold value and the user's currentglucose measurement value 1802 is less than the SET value. At time t₂,the monitoring application 1116 automatically operates the output userinterface element(s) 1120 to generate or otherwise provide one or morelow glucose notifications when the current glucose measurement value1802 is less than or equal to the SPT value. While the current glucosemeasurement value 1802 is less than the SPT value, the monitoringapplication 1116 may progressively escalate or otherwise increase thenumber and/or intensity of the user notifications in the absence ofreceiving an acknowledgment or other response from the user. At time t₃,once the current suspend duration reaches the maximum suspension timeperiod of two hours, the monitoring application 1116 automaticallysignals the command generation application 1114 and/or the motor controlmodule 512 to resume operating in a delivery mode. The monitoringapplication 1116 also sets the refractory period to the maximumrefractory time period of four hours while continuing to generate lowglucose user notifications or generating an urgent resume notificationin addition to and/or in alternative to the low glucose notifications.

At time t₄, in response to receiving an acknowledgment or response tothe user notifications from the user (e.g., the user clears or otherwiseacknowledges the urgent resume notification), the monitoring application1116 dynamically adjusts the refractory period from the maximumrefractory time period of four hours to the minimum delivery time periodof thirty minutes. Thereafter, at time t₅, once the minimum deliverytime period has elapsed since time t₃, the monitoring application 1116automatically signals the command generation application 1114 and/or themotor control module 512 to revert to the suspend delivery mode whileboth the user's predicted blood glucose value is less than thepredictive suspend threshold value and the user's current glucosemeasurement value 1802 is less than the SET value.

Turning to the graph 1900 of FIG. 19, at time t₁, the monitoringapplication 1116 automatically operates the infusion device 502 in asuspend delivery mode when both the user's predicted blood glucose valueis less than the predictive suspend threshold value and the user'scurrent glucose measurement value 1902 is less than the SET value. Attime t₂, once the current suspend duration reaches the maximumsuspension time period of two hours, the monitoring application 1116automatically signals the command generation application 1114 and/or themotor control module 512 to resume operating in a delivery mode and setsthe refractory period to the maximum refractory time period of fourhours. At time t₃, when the user's current glucose measurement value1902 is less than the SPT value while in the delivery mode and beforethe maximum refractory period has elapsed, the monitoring application1116 may automatically generate or otherwise provide one or more lowblood glucose user notifications via the output user interfaceelement(s) 1120.

At time t₄, in response to receiving an acknowledgment or response tothe low blood glucose notification, the monitoring application 1116dynamically adjusts the refractory period from the maximum refractorytime period of four hours to the minimum delivery time period of thirtyminutes. Substantially immediately thereafter (e.g., on the nextiteration of the delivery resumption process 1300), the monitoringapplication 1116 determines that the difference between time t₄ and timet₂ is greater than the minimum delivery time period (i.e., the adjustedrefractory time period) and automatically signals the command generationapplication 1114 and/or the motor control module 512 to revert to thesuspend delivery mode when both the user's predicted blood glucose valueis less than the predictive suspend threshold value and the user'scurrent glucose measurement value 1902 is less than the SET value.

FIG. 20 depicts an exemplary IOB monitoring process 2000 suitable forimplementation by a control system associated with a fluid infusiondevice, such as the pump control system 520, 1100 in the infusion device502, to automatically operate the fluid infusion device to deliver fluidin a manner that regulates or otherwise controls the active amount offluid (e.g., the JOB) in the body of a user (or patient). In thisregard, in various situations, when the infusion rate is reduced to zero(e.g., in response to meal-related glucose fluctuations, erroneousand/or invalid glucose sensor measurement values, or the like) orsuspended as described above in connection with delivery suspensionprocess 1200, the active amount of fluid in the body of the user becomesdepleted as the fluid is metabolized by the user's body. For example,when a current blood glucose measurement for the user that is fed backto the input of a closed-loop control system is below a target bloodglucose reference value (or glucose setpoint), the closed-loop controlsystem may output a delivery command of zero (since insulin cannot beremoved from the user's body) until the user's current glucosemeasurement begins increasing towards and/or above the target value.During this time period, any remaining active insulin in the user's bodyis gradually being metabolized. Depending on how long the insulindelivery rate is equal to zero or infusion is otherwise suspended, theuser's IOB may be relatively low (and potentially depleted completely)before insulin infusion is resumed when the user's current glucosemeasurement exceeds the target glucose value. The delay between when theuser's IOB goes low or becomes depleted and when insulin delivery isresumed is further compounded by the delay between when insulin isinfused and when the insulin is metabolized and begins to affect theuser's glucose levels. As a result, the user's glucose level could beundesirably high before the infused insulin takes effect. Accordingly,to reduce the likelihood of a hyperglycemic event in response to periodsof reduced and/or suspended insulin delivery, the IOB monitoring process2000 monitors and detects when the user's current IOB falls below adesired threshold amount and initiates an IOB control process toregulate the user's IOB, as described in greater detail below in thecontext of FIG. 21 and FIGS. 23-24.

Still referring to FIG. 20, the various tasks performed in connectionwith the IOB monitoring process 2000 may be performed by hardware,firmware, software executed by processing circuitry, or any combinationthereof. For illustrative purposes, the following description may referto elements mentioned above in connection with FIGS. 1-7 and 11. Inpractice, portions of the IOB monitoring process 2000 may be performedby different elements of the control system 500, such as, for example,the infusion device 502, the sensing arrangement 504, the pump controlsystem 520, 1100, the pump control module 1102, the motor control module512, and/or the motor 507. It should be appreciated that the IOBmonitoring process 2000 may include any number of additional oralternative tasks, the tasks need not be performed in the illustratedorder and/or the tasks may be performed concurrently, and/or the IOBmonitoring process 2000 may be incorporated into a more comprehensiveprocedure or process having additional functionality not described indetail herein. Moreover, one or more of the tasks shown and described inthe context of FIG. 20 could be omitted from a practical embodiment ofthe IOB monitoring process 2000 as long as the intended overallfunctionality remains intact.

Depending on the embodiment, the IOB monitoring process 2000 may beimplemented independently or integrated with the delivery resumptionprocess 1300 of FIG. 13. For example, the IOB monitoring process 2000may be performed during operation of the infusion device 502 in a normalclosed-loop delivery mode to detect and respond to low IOB that resultsfrom a closed-loop control system generating delivery commands thatresult in a relatively low infusion rate or an infusion rate of zeroover a period of time (e.g., when the user's current glucose values arebelow a target glucose value) when the closed-loop delivery mode is notsuspended. In such embodiments, upon suspension of delivery, the IOBmonitoring process 2000 may also be performed concurrently to thedelivery resumption process 1300 while the infusion device 502 isoperated in a suspend delivery mode, in which case task 1322 may beabsent from delivery resumption process 1300. In alternativeembodiments, the IOB monitoring process 2000 may be integrated into thedelivery resumption process 1300 (e.g., at task 1322), such that the JOBcontrol process 2100 of FIG. 21 is only performed when resuming deliveryfrom a suspend delivery mode based on the user's current JOB.

The illustrated IOB monitoring process 2000 initializes or otherwisebegins by obtaining, identifying or otherwise determining a desiredminimum IOB threshold value for the user (task 2002). In accordance withone or more embodiments, the minimum JOB threshold value isuser-configurable. For example, the patient or another user (e.g., adoctor or other trained medical personnel) may manipulate or otherwiseoperate an input user interface element 1120 to input or otherwiseprovide, to the monitoring application 1116, an IOB value below whichthe user would like to minimize his or her exposure to in order to avoidpotential hyperglycemic rebound events. In response to receiving aninput IOB protection value via a input user interface element 1120, themonitoring application 1116 may store or otherwise maintain the obtainedJOB protection value in memory 1106 (e.g., in a dedicated register) foruse as the minimum IOB threshold value. In other embodiments, theminimum JOB threshold value may be fixed and maintained in memory 1106in a manner that does not allow the minimum IOB threshold value to beadjusted using the user interface element(s) 1120.

In yet other embodiments, the minimum IOB threshold value is calculatedor otherwise determined by the monitoring application 1116 based on thenominal basal rate of insulin delivery that is or has been implementedby the command generation application 1114. For example, the monitoringapplication 1116 may calculate the minimum IOB threshold value bymultiplying the nominal basal infusion rate by a conversion factorhaving a magnitude less than one (e.g., 0.2 or 20%) and then applyingthe final value theorem for the IOB resulting from that reduced basalrate to arrive at a corresponding steady-state IOB value, as describedin greater detail below. It should be noted that in some embodiments,the monitoring application 1116 may continuously monitor the basaldelivery rate implemented by the command generation application 1114while in a normal closed-loop delivery mode and dynamically calculatethe nominal basal delivery rate and the corresponding minimum IOBthreshold value substantially in real-time, such that the minimum IOBthreshold value reflects changes to the user's insulin response and/orinsulin requirements over time. Additionally, in some embodiments, themonitoring application 1116 may account for manual boluses of insulindelivered in addition to the basal infusion rate to determine an overallnominal infusion rate for the user that reflects the user's historicalinsulin requirements. In alternative embodiments, a user may input orotherwise provide a minimum insulin infusion rate or a preprogrammedbasal infusion rate, which may be utilized by the command generationapplication 1114 and/or the monitoring application 1116 to determine acorresponding minimum IOB threshold value. In yet other embodiments, themonitoring application 1116 may calculate the minimum IOB thresholdvalue based on a minimum infusion rate imposed by the normal deliverymode implemented by the infusion device 502. Other factors that may beused to calculate a minimum IOB threshold value for a user may include,but are not limited to, the user's age, weight, fitness level, activitylevel, and/or other patient-specific characteristics or parameters.

Still referring to FIG. 20, the IOB monitoring process 2000 continues byobtaining, identifying or otherwise determining the current IOB for theuser (task 2004). For example, in one or more embodiments, themonitoring application 1116 calculates or otherwise determines theuser's current IOB based on any insulin delivered (e.g., the insulinautomatically delivered as a result of the delivery control schemeimplemented by the command generation application 1114 and anymanually-initiated boluses of insulin) using the appropriatepharmacokinetics/pharmacodynamics model corresponding to the user'sinsulin response (e.g., using time constants corresponding to the user'sinsulin response). In other embodiments, the current IOB may becalculated by the command generation application 1114 or elsewherewithin the control system 500 and/or the pump control system 520, 1100and obtained therefrom by the monitoring application 1116. As describedin greater detail below, depending on the embodiment, the current IOBmay be calculated as the current IOB in the subcutaneous compartment,the current IOB in the plasma compartment plus the current IOB in thesubcutaneous compartment, or the current IOB in the effect sitecompartment plus the current IOB in both the plasma compartment and thesubcutaneous compartment. That said, the subcutaneous compartment willbe the first of those compartments to be depleted of insulin after aprolonged period of zero insulin infusion, and accordingly, the subjectmatter may be described in the context of the current IOB in thesubcutaneous compartment for purposes of explanation.

After obtaining the minimum IOB threshold value for the user and thecurrent IOB value for the user, the IOB monitoring process 2000 comparesthe user's current IOB value to the minimum IOB threshold value todetect, identify, or otherwise determine whether the user's current IOBvalue is less than the minimum IOB threshold value (task 2006). When theuser's current IOB value is greater than the minimum IOB thresholdvalue, the IOB monitoring process 2000 maintains operating the infusiondevice in its current operating mode (task 2008). In this regard, if thecommand generation application 1114 and/or the motor control module 512are currently implementing a suspend delivery mode and the monitoringapplication 1116 determines the user's current IOB value is greater thanthe minimum IOB threshold value, the monitoring application 1116maintains the command generation application 1114 and/or the motorcontrol module 512 in the suspend delivery mode, such that any deliverycommands that would otherwise be generated by the command generationapplication 1114 are disabled or otherwise ineffectual (subject to thedelivery resumption process 1300). Similarly, if the command generationapplication 1114 is currently implementing a closed-loop delivery modeand the monitoring application 1116 determines the user's current IOBvalue is greater than the minimum IOB threshold value, the monitoringapplication 1116 maintains the command generation application 1114 inthe closed-loop delivery mode, such that any delivery commands generatedby the command generation application 1114 are provided to the motorcontrol module 512 without being modified or otherwise overridden.

When the user's current IOB value is less than the minimum IOB thresholdvalue, the IOB monitoring process 2000 initiates operating the infusiondevice in an alternative (or adjusted) delivery mode configured toregulate the user's IOB to at least the minimum IOB threshold value(task 2010). In this regard, if the command generation application 1114and/or the motor control module 512 are currently implementing a suspenddelivery mode and the monitoring application 1116 determines the user'scurrent IOB value is less than the minimum IOB threshold value, themonitoring application 1116 automatically signals, commands, orotherwise instructs the command generation application 1114 and/or themotor control module 512 to resume implementing a delivery mode in asimilar manner as described above in the context of FIGS. 13-19.Additionally, in some embodiments, the monitoring application 1116 mayalso automatically operate an output user interface element 1120 togenerate or otherwise provide a notification to the user that deliveryis being resumed based on the user's current IOB falling below theuser's minimum IOB threshold value, in a similar manner as describedabove in the context of FIGS. 13-19.

It should be noted that in some embodiments, when transitioning from thesuspend delivery mode, the delivery mode initiated by the IOB monitoringprocess 2000 may be subject to the minimum suspension time periodimposed by the automatic delivery suspension (e.g., task 1314), while inother embodiments, the IOB monitoring process 2000 may not be subject tothe minimum suspension time period. Similarly, in some embodiments,after transitioning from the suspend delivery mode, the IOB monitoringprocess 2000 may be subject to the refractory time period imposed by thedelivery suspension process 1200 (e.g., task 1206), such that themonitoring application 1116 maintains operation of the infusion devicein the IOB control delivery mode for at least the minimum delivery timeperiod even if the user's current IOB has met or exceeded the minimumIOB threshold value.

As described in greater detail below in the context of FIG. 21, inaccordance with one or more embodiments, the difference between theuser's current IOB and the minimum IOB threshold value is utilized tocalculate or otherwise determine an alternative delivery command forregulating the user's current IOB to the minimum IOB threshold value.The alternative delivery command may be utilized to augment, adjust, orotherwise replace the normal delivery command generated in accordancewith the normal delivery control mode implemented by the commandgeneration application 1114 and/or pump control system 520, 1100. Insome embodiments, the greater of the alternative delivery command andthe normal delivery command may be provided to the motor control module512. However, in alternative embodiments, the alternative deliverycommand may be weighted or otherwise combined with the normal deliverycommand to achieve an augmented delivery command that achieves a desiredtradeoff between regulating the user's blood glucose and regulating theuser's JOB. For example, the alternative delivery command and the normaldelivery command may be averaged to achieve an augmented deliverycommand that balances regulating the user's blood glucose withregulating the user's JOB. The monitoring application 1116 maintainsoperation of the infusion device in a manner that is influenced by thealternative delivery command at least until the user's current IOB isgreater than or equal to minimum IOB threshold value. Thereafter, themonitoring application 1116 may cause operation of the infusion device502 to revert back to the suspend delivery mode pursuant to the deliverysuspension process 1200 or otherwise maintain operation of the infusiondevice 502 in the normal delivery mode.

FIG. 21 depicts an exemplary IOB control process 2100 suitable forimplementation by a control system associated with a fluid infusiondevice, such as the pump control system 520, 1100 in the infusion device502, in conjunction with the IOB monitoring process 2000 toautomatically regulate the user's IOB to a desired value (e.g., theminimum IOB threshold value). The various tasks performed in connectionwith the IOB control process 2100 may be performed by hardware,firmware, software executed by processing circuitry, or any combinationthereof. For illustrative purposes, the following description may referto elements mentioned above in connection with FIGS. 1-7 and 11. Inpractice, portions of the IOB control process 2100 may be performed bydifferent elements of the control system 500, such as, for example, theinfusion device 502, the sensing arrangement 504, the pump controlsystem 520, 1100, the pump control module 1102, the motor control module512, and/or the motor 507. It should be appreciated that the IOB controlprocess 2100 may include any number of additional or alternative tasks,the tasks need not be performed in the illustrated order and/or thetasks may be performed concurrently, and/or the IOB control process 2100may be incorporated into a more comprehensive procedure or processhaving additional functionality not described in detail herein.Moreover, one or more of the tasks shown and described in the context ofFIG. 21 could be omitted from a practical embodiment of the IOB controlprocess 2100 as long as the intended overall functionality remainsintact.

In the illustrated embodiment, the IOB control process 2100 begins byobtaining, calculating or otherwise determining a baseline or referencedelivery command for operating the infusion device based at least inpart on the current glucose measurement value using the normal controlscheme for when the infusion device is in a delivery mode (task 2102).In this regard, the command generation application 1114 may utilize thecurrent glucose measurement value obtained via the sensing arrangement504 in accordance with the normal control scheme implemented by thecommand generation application 1114. For example, the command generationapplication 1114 may determine a difference between the current glucosemeasurement value and a target glucose value (e.g., the glucosesetpoint) and input or otherwise provide the difference to a closed-loopcontrol system to obtain a closed-loop delivery command configured toregulate the current glucose measurement value to the target bloodglucose value by minimizing the difference between the current glucosemeasurement value and the target value.

FIG. 22 depicts an exemplary embodiment of a closed-loop control system2200 that may be implemented by the pump control system 520, 1100 and/orthe command generation application 1114 associated with an infusiondevice 502 to operate the motor 507 of the infusion device 502 andregulate glucose levels in the body 518 of the user. It should be notedthat FIG. 22 is a simplified representation of the closed-loop controlsystem 2200 for purposes of explanation and is not intended to limit thesubject matter described herein in any way. Practical embodiments of theclosed-loop control system 2200 may include any number of controlparameters configured to compensate, correct, or otherwise account forvarious operating conditions experienced and/or exhibited by theinfusion device 502 and/or the sensing arrangement 504, such as, forexample, one or more patient-specific control parameters (e.g., aninsulin sensitivity factor, a daily insulin requirement, an insulinlimit, a reference basal rate, a reference fasting glucose, an activeinsulin action duration, pharmacodynamical time constants, or the like).Various implementation details pertaining to determining gaincoefficients and providing closed-loop control are described in greaterdetail in U.S. Pat. No. 7,402,153 or U.S. patent application Ser. No.13/966,120, each of which is incorporated by reference herein in itsentirety.

The closed-loop control system 2200 receives or otherwise obtains thetarget glucose value at input 2202. In exemplary embodiments, the targetglucose value is stored or otherwise maintained in memory 1106, however,in some alternative embodiments, the target value may be received froman external component (e.g., CCD 106 and/or computer 108). Theclosed-loop control system 2200 receives or otherwise obtains thecurrent glucose measurement value at input 2204 and calculates orotherwise determines the difference (or error signal) between thecurrent glucose measurement value and the target glucose value atsummation block 2206 (e.g., by subtracting the target glucose value fromthe current glucose measurement value). The difference output by thesummation block 2206 is provided to each of a proportional term path, anintegral term path, and a derivative term path. The proportional termpath includes a gain block 2210 that multiplies the difference by aproportional gain coefficient, K_(P), to obtain the proportional term.The integral term path includes an integration block 2212 thatintegrates the difference and a gain block 2214 that multiplies theintegrated difference by an integral gain coefficient, K_(I), to obtainthe integral term. The derivative term path includes a derivative block2216 that determines the derivative of the difference and a gain block2218 that multiplies the derivative of the difference by a derivativegain coefficient, K_(D), to obtain the derivative term. The proportionalterm, the integral term, and the derivative term are then added orotherwise combined to obtain a delivery command at output 2208, which,in turn, may be provided to the motor control module 512 for operatingthe motor 507. In exemplary embodiments, the delivery command at theoutput 2208 is configured to reduce or otherwise minimize the differencedetermined at the summation block 2206 to zero. In practice, the PIDgain coefficients may be stored or otherwise maintained in memory 1106for reference by the command generation application 1114 when generatingthe delivery command. In one embodiment, the integral gain coefficientmay be equal to (or represented as) the proportional gain coefficientdivided by an integral time

$\left( {{e.g.},{K_{I} = \frac{K_{P}}{\tau_{I}}}} \right)$while the derivative gain coefficient may be equal to the proportionalgain coefficient multiplied by a derivative time constant (e.g.,K_(D)=τ_(D)K_(D)).

Referring again to FIG. 21, with continued reference to FIGS. 1-7, 11and 22, the illustrated IOB control process 2100 continues bydetermining, verifying, or otherwise confirming whether or not thedelivery command is greater than or equal to zero, and operating theinfusion device in accordance with the normal delivery command when thedelivery command is greater than zero (tasks 2104, 2106). In thisregard, the delivery command generated by the closed-loop control system2200 at the output 2208 will be greater than or equal zero when thecurrent glucose measurement value from the sensing arrangement 504 atinput 2204 is greater than or equal to the target blood glucose value atinput 2202, in which case, the command generation application 1114and/or the monitoring application 1116 enables or otherwise provides thedelivery command at the output 2208 to the motor control module 512 tooperate the motor 507 to deliver insulin to the body 518 of the user andregulate the user's glucose levels to the target value.

When the normal delivery command is less than zero, the IOB controlprocess 2100 continues by calculating or otherwise determining analternative delivery command for operating the infusion device based atleast in part on the difference between the user's current IOB value andthe minimum IOB threshold value (task 2108). In this regard, thealternative delivery command (also referred to herein as the IOBdelivery command) is configured to regulate the user's current IOB tothe minimum IOB threshold value, and thereby, reduce the likelihood ofhyperglycemic rebound event after the user's glucose level begins torise. As described in greater detail below, in an exemplary embodiment,an alternative closed-loop control system is implemented to regulate thedifference between the user's current IOB value and the minimum IOBthreshold value to be equal to zero.

The IOB control process 2100 continues by determining, verifying, orotherwise confirming whether or not the IOB delivery command is greaterthan or equal to zero, and operating the infusion device in accordancewith the IOB delivery command when the IOB delivery command is greaterthan zero (tasks 2110, 2112). In this regard, the IOB delivery commandgenerated by the command generation application 1114 and/or monitoringapplication 1116 will be greater than or equal zero when the user'scurrent IOB value is less than or equal the minimum IOB threshold value,in which case, the command generation application 1114 and/or themonitoring application 1116 enables or otherwise provides IOB deliverycommand to the motor control module 512 to operate the motor 507 todeliver insulin to the body 518 of the user and regulate the user's IOBto the minimum IOB threshold value. When both the normal deliverycommand and the IOB delivery command are less than zero, the IOB controlprocess 2100 may terminate or exit without operating the infusion deviceto deliver insulin to the user (e.g., because both the user's bloodglucose is below the target value and the user's current IOB is abovethe minimum IOB threshold).

It should be noted that FIG. 21 merely depicts one exemplaryimplementation of an IOB control process 2100, and in practice, thealternative IOB delivery command may be determined in any number ofalternative manners. In this regard, in embodiments where both thenormal delivery command and the IOB delivery command are greater thanzero, the normal delivery command may be adjusted or otherwise modifiedusing the IOB delivery command to achieve a desired tradeoff betweenregulating the user's blood glucose and regulating the user's JOB. Forexample, the normal delivery command and the IOB delivery command may beaveraged together or otherwise combined using various weightingparameters and/or weighting functions to obtain an adjusted deliverycommand.

IOB Control

As described above in the context of FIGS. 20-21, to reduce thelikelihood of hyperglycemic rebound events, the current IOB for the useris determined on a substantially continuous basis and monitoredsubstantially in real-time to detect or otherwise identify when theuser's IOB falls below a desired minimum threshold. In this regard, thecurrent IOB is determined based on all insulin delivered, which includesmanual boluses of insulin. Assuming an infusion rate u_(a)(t) in unitsper hour (U/h), a pharmacokinetic model for the subcutaneous infusion ofinsulin is given by the following ordinary differential equations:

${{{\overset{.}{I}}_{S}(t)} = {{{- \frac{1}{\tau_{1}}}{I_{S}(t)}} + {\frac{1}{\tau_{1}}{u_{a}(t)}}}},{{{\overset{.}{I}}_{P}(t)} = {{{- \frac{1}{\tau_{2}}}{I_{P}(t)}} + {\frac{1}{\tau_{2}}{I_{S}(t)}}}},{and}$${{{\overset{.}{I}}_{E}(t)} = {{{- \frac{1}{\tau_{3}}}{I_{E}(t)}} + {\frac{1}{\tau_{3}}{I_{P}(t)}}}},$where I_(S)(t) corresponds to the subcutaneous compartment, I_(P)(t)corresponds to the subcutaneous plus plasma compartment, I_(E)(t)corresponds to the effect site compartment, u_(a)(t) includes orotherwise accounts for both basal and bolus infusions, and the τ_(n)terms are the respective time constants associated therewith. Forexample, for a rapid-acting insulin such as aspart, τ₁= 50/60, τ₂= 70/60h, and τ₃= 55/60 h.

The total insulin on board can be calculated using one or more of thecompartments using equations:

IOB₁(t) = ∫₀^(t)U_(a)(τ)d τ − ∫₀^(t)I_(S)(τ)d τ, IOB₂(t) = ∫₀^(t)U_(a)(τ)d τ − ∫₀^(t)I_(P)(τ)d τ, andIOB₃(t) = ∫₀^(t)U_(a)(τ)d τ − ∫₀^(t)I_(E)(τ)d τ,where IOB₁(t) corresponds to the insulin on board in the subcutaneouscompartment, IOB₂(t) corresponds to the insulin on board in the plasmacompartment, and IOB₃(t) corresponds to the insulin on board in allthree compartments. These equations can be rewritten in the Laplacedomain as:

${{{IOB}_{1}(s)} = {\frac{\tau_{1}}{\left( {{\tau_{1}s} + 1} \right)}{U_{a}(s)}}},{{{IOB}_{2}(s)} = {\frac{{\tau_{1}\tau_{2}s} + \tau_{1} + \tau_{2}}{\left( {{\tau_{1}s} + 1} \right)\left( {{\tau_{2}s} + 1} \right)}{U_{a}(s)}}},{and}$${{IOB}_{3}(s)} = {\frac{{\tau_{1}\tau_{2}\tau_{3}s^{2}} + {\left( {{\tau_{1}\tau_{2}} + {\tau_{1}\tau_{3}} + {\tau_{2}\tau_{3}}} \right)s} + \tau_{1} + \tau_{2} + \tau_{3}}{\left( {{\tau_{1}s} + 1} \right)\left( {{\tau_{2}s} + 1} \right)\left( {{\tau_{3}s} + 1} \right)}{{U_{a}(s)}.}}$

For purposes of explanation, the subject matter may be described hereinin terms of the insulin on board in the subcutaneous compartment (IOB₁)because the subcutaneous compartment will be the first compartment to bedepleted of insulin after prolonged periods of zero insulin infusion,and thus, is the first compartment to be maintained at the desiredminimum JOB.

The minimum IOB threshold value for the insulin on board may becalculated based on the lowest desirable insulin infusion rate. Forexample, the minimum IOB threshold value for the IOB in the subcutaneouscompartment may be calculated or otherwise determined using the equationIOB_(min)=τ₁u_(min) by applying the final value theorem to the equationfor IOB₁(s), where u_(min) corresponds to a steady state rate equal tothe minimum desirable insulin infusion rate. As described above in thecontext of FIG. 20, the minimum desirable insulin infusion rate may bedetermined as a minimum insulin infusion rate input by a user orcalculated based on the nominal basal delivery rate implemented by thecommand generation application 1114, a preprogrammed basal deliveryrate, a historical average delivery rate for the user, or otherhistorical data indicative of the user's insulin requirements. Forexample, if the nominal basal delivery rate is equal to 1 U/h, themonitoring application 1116 may multiply the nominal basal delivery rateby a factor of 0.2 to determine a minimum infusion rate of 0.2 U/h,resulting in a minimum IOB threshold value for the subcutaneouscompartment equal to one sixth of a unit as a steady state result of thefinal value theorem. To regulate the current IOB in the subcutaneouscompartment to the minimum IOB threshold value, a closed-loopproportional-integral control system may be configured to determine anIOB delivery command by implementing the following equation:

${{u_{IOB}(t)} = {K_{P_{\min}}\left( {{e_{IOB}(t)} + {\frac{1}{\tau_{1_{\min}}}{\int_{0}^{t}{{e_{IOB}(\tau)}d\;\tau}}}} \right)}},$where e_(IOB)(t) is an error signal representing the difference betweenthe current IOB and the minimum IOB threshold value (e.g.,e_(IOB)(t)=IOB_(min)−IOB₁(t)), K_(P) _(min) is the proportional gaincoefficient for regulating the user's IOB to the minimum IOB thresholdvalue, and τ₁ _(min) is the integral time constant for regulating theuser's IOB to the minimum IOB threshold value. In this regard, K_(P)_(min) and τ₁ _(min) may be tuned to achieve the desired response.

In alternative embodiments, instead of implementing a closed-loopproportional-integral control scheme to regulate the user's IOB to theminimum IOB threshold value, the IOB delivery command may be configuredto provide a constant rate of infusion. For example, in one or moreembodiments, the IOB delivery command may be fixed or otherwise set at afraction of the basal delivery rate (e.g., 20% of the nominal basaldelivery rate). In such embodiments, the response to the differencebetween the current IOB and the minimum IOB threshold value may beslower than it would be using the closed-loop proportional-integralcontrol scheme (e.g., a longer amount of time required for the user'scurrent IOB in the subcutaneous compartment to reach the minimum IOBthreshold value), however, the complexity of implementation is reducedrelative to the closed-loop control scheme.

As described above in the context of FIG. 21, the IOB delivery command(u_(IOB)(t)) is provided to the motor control module 512 when the user'scurrent IOB is less than the minimum IOB threshold value to maintain theuser's IOB at or near the minimum IOB threshold value and reduce thelikelihood of a hyperglycemic event by preventing a total depletion ofinsulin on board. In this manner, the IOB control process 2100 inconjunction with the IOB monitoring process 2000 ensures the user hasinsulin on board, similar to healthy normal glucose tolerant users whogenerally always have insulin on board by virtue of healthy pancreaticfunction.

FIGS. 23-24 depict graphs of the IOB for the various compartments alongwith the corresponding infusion rate resulting from the IOB monitoringprocess 2000 of FIG. 20 and the IOB control process 2100 of FIG. 21being implemented in conjunction with the delivery suspension process1200 and the delivery resumption process 1300 of FIG. 13 using the aboveequations for determining the IOB delivery command. In this regard,FIGS. 23-24 depict a scenario where the nominal basal infusion rate isequal to 1 U/h, u_(min)=0.2 U/h (e.g., by multiplying the nominal basaldelivery rate by a factor of 0.2), τ₁= 50/60 h, IOB_(min)=⅙ U for thesubcutaneous compartment, K_(P) _(min) =20 h⁻¹, and τ₁ _(min) =1 h. Asillustrated, after operating in the normal delivery mode forapproximately one hour, the monitoring application 1116 mayautomatically suspend delivery at time t₁ based on the user's glucosevalues falling below their applicable suspend thresholds and/or theclosed-loop control system 2200 implemented by the command generationapplication 1114 may generate delivery commands equal to zero based onthe user's current glucose measurement value being less than the targetglucose value. At time t₂, the monitoring application 1116 detects orotherwise identifies that the user's IOB in the subcutaneous compartmentis less than or equal to the minimum IOB threshold value for thesubcutaneous compartment (e.g., IOB_(min)=⅙ U), and thereafter, thecommand generation application 1114 and/or the monitoring application1116 generates an alternative delivery command configured to regulatethe user's IOB in the subcutaneous compartment to the minimum IOBthreshold value (e.g., by providing an infusion rate of 0.2 U/h).Thereafter, at time t₃, when the monitoring application 1116automatically resumes delivery based on the user's glucose valuesexceeding their applicable resume thresholds and/or the control schemeimplemented by the command generation application 1114 generatesdelivery commands greater than zero (or greater than the IOB deliverycommand), the normal delivery commands are provided to the motor controlmodule 512 and utilized to operate the motor 507 in lieu of the IOBdelivery commands. As illustrated in FIG. 24, when the user's IOB in thesubcutaneous compartment exceeds the minimum IOB threshold as a resultof the increased infusion rate, the IOB delivery command generated basedon the user's IOB is reduced to zero.

It should be noted that the IOB control described herein in the contextof FIGS. 20-21 and FIGS. 23-24 may be utilized to augment or otherwisesupplement the normal glucose control and/or the delivery suspensionprocess 1200 in situations where the sensing arrangement 504 isproviding invalid or unusable measurement values, providing erroneouslow glucose measurement values, or is otherwise functioning improperly.In such situations, the likelihood of hyperglycemic events is reduced byensuring that at least some minimum amount of IOB is present and beingmetabolized in the user's body.

FIG. 25 depicts an exemplary IOB suspension process 2500 suitable forimplementation by a control system associated with a fluid infusiondevice, such as the pump control system 520, 1100 in the infusion device502, in conjunction with an open-loop basal delivery mode to reduce thelikelihood of a hypoglycemic event. The various tasks performed inconnection with the IOB suspension process 2500 may be performed byhardware, firmware, software executed by processing circuitry, or anycombination thereof. For illustrative purposes, the followingdescription may refer to elements mentioned above in connection withFIGS. 1-7 and 11. In practice, portions of the IOB suspension process2500 may be performed by different elements of the control system 500,such as, for example, the infusion device 502, the sensing arrangement504, the pump control system 520, 1100, the pump control module 1102,the motor control module 512, and/or the motor 507. It should beappreciated that the IOB suspension process 2500 may include any numberof additional or alternative tasks, the tasks need not be performed inthe illustrated order and/or the tasks may be performed concurrently,and/or the IOB suspension process 2500 may be incorporated into a morecomprehensive procedure or process having additional functionality notdescribed in detail herein. Moreover, one or more of the tasks shown anddescribed in the context of FIG. 25 could be omitted from a practicalembodiment of the IOB suspension process 2500 as long as the intendedoverall functionality remains intact.

In exemplary embodiments, the IOB suspension process 2500 is performedupon entering an open-loop basal delivery mode to delay or otherwisesuspend basal infusion in situations where there is sufficient insulinyet to be metabolized by the user and infusion of insulin may increasethe likelihood of a hypoglycemic event. The IOB suspension process 2500initializes or otherwise begins by obtaining, identifying or otherwisedetermining a basal steady-state IOB threshold value for the user (task2502). In a similar manner as described above in the context of FIG. 20with respect to the minimum IOB threshold value, the basal steady-stateIOB threshold value may be user-configurable and stored or otherwisemaintained in memory 1106. Alternatively, the basal steady-state IOBthreshold value may be calculated or otherwise determined as the maximumIOB likely to result from delivery at the basal infusion rate. Forexample, the monitoring application 1116 may calculate the basalsteady-state IOB threshold value by applying the final value theorem forthe IOB resulting from that the nominal basal infusion rate (e.g., 1U/h) to arrive at a corresponding steady-state IOB value. Again, in asimilar manner as described above, the monitoring application 1116 maycontinuously monitor the basal delivery rate implemented by the commandgeneration application 1114 while in a normal closed-loop delivery modeand dynamically calculate the nominal basal delivery rate and thecorresponding basal steady-state IOB threshold value substantially inreal-time and/or in a manner that accounts for manual boluses of insulindelivered in addition to the basal infusion rate.

The IOB suspension process 2500 continues by obtaining, identifying orotherwise determining the current IOB for the user (task 2504) in asimilar manner as described above in the context of IOB monitoringprocess 2000 and comparing the user's current IOB value to the basalsteady-state IOB threshold value to detect, identify, or otherwisedetermine whether the user's current IOB value is greater than the basalsteady-state IOB threshold value (task 2506). In this regard, when theuser's current IOB is greater than the basal steady-state IOB thresholdvalue, the IOB suspension process 2500 continues by suspending orotherwise disabling the open-loop delivery commands (task 2508). In thisregard, the loop defined by tasks 2504, 2506, and 2508 repeatsindefinitely upon transitioning into the open-loop basal delivery modefrom a closed-loop delivery mode until the current IOB is less than thebasal steady-state IOB threshold value. When the user's current IOB isless than or equal to the basal steady-state IOB threshold value, theIOB suspension process 2500 enables or otherwise allows the open-loopdelivery commands to be utilized to operate the motor of the infusiondevice to deliver fluid at the basal infusion rate (task 2510).

In alternative embodiments, the IOB suspension process 2500 maycalculate or otherwise determine a duration of time for which theopen-loop basal delivery commands should be suspended based on thedifference between the user's current IOB and the basal steady-state IOBthreshold value (e.g., the amount of time required for user's currentIOB to exponentially decay to the basal steady-state IOB thresholdvalue). In such embodiments, rather than repeating the loop defined bytasks 2504, 2506 and 2508, the IOB suspension process 2500 may suspendor otherwise disable the open-loop delivery commands for that amount ofexponential decay time at task 2508 before enabling the open-loopdelivery commands at task 2510.

FIG. 26 depict graphs of a measured glucose value along with acorresponding graph of a user's IOB in FIG. 27, and FIG. 28 depicts acorresponding graph of the infusion rate implemented by the pump controlsystem 520, 1100 in conjunction with the IOB suspension process 2500 ofFIG. 25. Prior to t₁, when the user's current glucose measurement valueis greater than the target glucose measurement value as depicted in FIG.26, the closed-loop control system 2200 generates delivery commandsbased on the difference between the current glucose measurement valueand the target glucose measurement value as depicted in FIG. 28, whichincreases the user's IOB as depicted in FIG. 27. After t₁, when theuser's current glucose measurement value is less than the target glucosemeasurement value, the closed-loop control system 2200 generatesdelivery commands equal to zero. At time t₂, when the pump controlsystem 520, 1100 determines that the infusion device 502 should betransitioned from the closed-loop delivery mode to an open-loop deliverymode (e.g., due to a failure to receive measurement values from thesensing arrangement 504), the IOB suspension process 2500 suspends orotherwise disables the open-loop delivery commands at time t₂ based onthe user's current IOB being greater than the basal steady-state IOBthreshold value, as depicted in FIGS. 27-28. In this regard, the IOBsuspension process 2500 suspends or otherwise disables the open-loopdelivery commands from time t₂ until time t₃ until the user's currentIOB reaches the basal steady-state IOB threshold value before resumingthe open-loop delivery commands at time t₃. As described above, in someembodiments, the duration of time that the open-loop delivery issuspended (e.g., t₃−t₂) may be calculated or otherwise predeterminedbased upon the difference between the user's current IOB and the basalsteady-state IOB threshold value at time t₂. As illustrated in FIGS.26-27, by virtue of the IOB suspension process 2500, the active IOB ismetabolized and the downward trend in the user's glucose may be slowedor otherwise settled before enabling the basal insulin infusion, therebyreducing the likelihood of a hypoglycemic event.

For the sake of brevity, conventional techniques related to glucosesensing and/or monitoring, closed-loop glucose control, sensorcalibration and/or compensation, and other functional aspects of thesubject matter may not be described in detail herein. In addition,certain terminology may also be used in the herein for the purpose ofreference only, and thus is not intended to be limiting. For example,terms such as “first”, “second”, and other such numerical termsreferring to structures do not imply a sequence or order unless clearlyindicated by the context. The foregoing description may also refer toelements or nodes or features being “connected” or “coupled” together.As used herein, unless expressly stated otherwise, “coupled” means thatone element/node/feature is directly or indirectly joined to (ordirectly or indirectly communicates with) another element/node/feature,and not necessarily mechanically.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. For example, the subject matter described herein isnot limited to the infusion devices and related systems describedherein. Moreover, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope defined by the claims, which includesknown equivalents and foreseeable equivalents at the time of filing thispatent application. Accordingly, details of the exemplary embodiments orother limitations described above should not be read into the claimsabsent a clear intention to the contrary.

What is claimed is:
 1. An infusion device comprising: a motor operableto deliver fluid to a body of a user, delivery resulting in active fluidinfluencing a physiological condition in the body of the user; and acontrol module coupled to the motor to operate the motor to deliver thefluid based on a difference between a current measurement value for thephysiological condition and a target value for the physiologicalcondition when the current measurement value is greater than the targetvalue, and when the current measurement value is less than or equal tothe target value, wherein the control module is configured to: operatethe motor to deliver the fluid to regulate a current amount of theactive fluid in the body of the user to a lower threshold amount for theactive fluid in the body of the user when the current amount is lessthan the lower threshold amount; and suspend operation of the motor whenthe current amount is greater than an upper threshold amount, and aftersuspending operation, automatically enable operation of the motor whenthe current amount of the active fluid in the body of the user is lessthan the lower threshold amount.
 2. The infusion device of claim 1, thefluid comprising insulin, wherein: the current measurement valuecomprises a current glucose measurement value for the user; the lowerthreshold amount comprises a minimum insulin on board; and the upperthreshold amount comprises a steady-state insulin on board resultingfrom a basal infusion rate.
 3. The infusion device of claim 1, whereinthe control module operates the motor to deliver the fluid to regulatethe current amount of the active fluid by determining a delivery commandusing equation${{u_{IOB}(t)} = {K_{P_{\min}}\left( {{e_{IOB}(t)} + {\frac{1}{\tau_{1_{\min}}}{\int_{0}^{t}{{e_{IOB}(\tau)}d\;\tau}}}} \right)}},$where u_(IOB)(t) represents the delivery command, e_(IOB)(t) representsa difference between the current amount of the active fluid and thelower threshold amount, K_(P) _(min) is a proportional gain coefficientfor regulating the current amount of the active fluid, and τ_(l) _(min)is an integral time constant for regulating the current amount of theactive fluid.
 4. The infusion device of claim 1, further comprising: auser interface element to receive an input insulin on board protectionvalue; and a data storage element, wherein the control module is coupledto the user interface element and the data storage element to store theinput insulin on board protection value in the data storage element foruse as the lower threshold amount.
 5. The infusion device of claim 1,wherein the control module is configured to continuously monitor a basaldelivery rate while in a normal closed-loop delivery mode, dynamicallycalculate a nominal basal delivery rate, and calculate the lowerthreshold amount based on the nominal basal delivery rate.
 6. Theinfusion device of claim 1, wherein the control module maintains aclosed-loop delivery mode when the current amount is greater than thelower threshold amount prior to initiating an alternative delivery modeto operate the motor to deliver the fluid to regulate the current amountof the active fluid in the body of the user to the lower thresholdamount once the current amount is less than the lower threshold amount.7. The infusion device of claim 1, wherein the control module maintainsoperation of the motor to deliver the fluid to regulate the currentamount of the active fluid in the body of the user to the lowerthreshold amount for a refractory period prior to suspending operationof the motor.
 8. The infusion device of claim 1, wherein the controlmodule operates the motor to deliver the fluid to regulate the currentamount of the active fluid in the body of the user to the lowerthreshold amount using an alternative closed-loop control systemconfigured to regulate a difference between the current amount of theactive fluid and the lower threshold amount to zero.
 9. The infusiondevice of claim 1, further comprising: a user interface element toreceive a basal steady-state insulin on board threshold value; and adata storage element, wherein the control module is coupled to the userinterface element and the data storage element to store the basalsteady-state insulin on board threshold value in the data storageelement for use as the upper threshold amount.
 10. The infusion deviceof claim 1, wherein the control module is configured to continuouslymonitor a basal delivery rate while in a normal closed-loop deliverymode, dynamically calculate a nominal basal delivery rate, and calculatethe upper threshold amount based on the nominal basal delivery rate. 11.The infusion device of claim 1, wherein the control module disablesopen-loop delivery commands until the current amount is less than theupper threshold amount and enables the open-loop delivery commands tooperate the motor when the current amount is less than the upperthreshold amount.
 12. The infusion device of claim 1, wherein thecontrol module determines a duration of time for which operation of themotor should be suspended based on a difference between the currentamount and the upper threshold amount.
 13. An infusion devicecomprising: a motor operable to deliver fluid to a body of a user,delivery resulting in active fluid influencing a physiological conditionin the body of the user; and a control module coupled to the motor to:automatically suspend operation of the motor to deliver the fluid to theuser based at least in part on a current measurement value for thephysiological condition of the user; determine a current amount ofactive fluid in the body of the user; and after automatically suspendingoperation of the motor: automatically resume operation of the motor todeliver the fluid to the user to regulate the current amount of activefluid to a lower threshold amount based on a difference between thecurrent amount of active fluid and the lower threshold amount when thecurrent measurement value for the physiological condition of the user isless than a threshold value for the physiological condition of the user;and automatically suspend operation of the motor when the current amountof active fluid is greater than an upper threshold amount.
 14. Theinfusion device of claim 13, the fluid comprising insulin, wherein: thecurrent measurement value comprises a current glucose measurement valuefor the user; the lower threshold amount comprises a minimum insulin onboard; and the upper threshold amount comprises a steady-state insulinon board resulting from a basal infusion rate.
 15. The infusion deviceof claim 13, the control module suspending operation of the motor basedon the current measurement value, wherein the control moduleautomatically enables operation of the motor when the current amount ofthe active fluid in the body of the user is less than the lowerthreshold amount.
 16. The infusion device of claim 13, wherein thethreshold value for the physiological condition of the user comprises atarget value for a closed-loop operating mode.
 17. The infusion deviceof claim 16, wherein the control module automatically resumes operationof the motor to deliver the fluid to the user to regulate the currentamount of active fluid to the lower threshold amount based on thedifference between the current amount of active fluid and the lowerthreshold amount when the current measurement value for thephysiological condition of the user is less than the target value andthe current amount of active fluid is less than at least one of thelower threshold amount and the upper threshold amount.
 18. An infusiondevice comprising: a motor operable to deliver fluid to a body of auser, delivery resulting in active fluid influencing a physiologicalcondition in the body of the user; and a control module coupled to themotor to: determine a current amount of active fluid in the body of theuser; automatically suspend operation of the motor to the fluid upontransitioning to an open-loop mode from a closed-loop mode regulating acurrent measurement value for the physiological condition of the user toa target value when the current amount of active fluid is greater thanan upper threshold amount; and after automatically suspending operationof the motor, automatically resume operation of the motor to deliver thefluid to the user to regulate the current amount of active fluid to alower threshold amount based on a difference between the current amountof active fluid and the lower threshold amount when the current amountof active fluid is less than the lower threshold amount.
 19. Theinfusion device of claim 18, the fluid comprising insulin, wherein: thecurrent measurement value comprises a current glucose measurement valuefor the user; the lower threshold amount comprises a minimum insulin onboard; and the upper threshold amount comprises a steady-state insulinon board resulting from a basal infusion rate.